Leukocyte overshoot: a new sign of bioincompatibility in fast hemodialysis

A high blood flow of 400 ml/min induces leukocytosis after 2 hr of dialysis with leukocyte concentrations of 110-150% of predialysis values. The leukocytosis occurs with both low and high biocompatible membranes, such as Cuprophan, Hemophan, and Polyamide. Cuprophan induces the most profound leukopenia, and also induces the most pronounced leukocytosis. For treatments with a given membrane there was, however, no correlation between leukopenia and leukocytosis. Leukopenia was independent of blood flow, while leukocytosis was strongly influenced by this factor. These observations indicate that different factors cause leukopenia and leukocytosis. Although a larger area induced more leukopenia, the effect was small. Membrane area had no effect on leukocytosis. There were no acute clinical side effects during dialysis that could be related to the leukocyte overshoot. The cause and chronic clinical consequences of leukocyte overshoot are unknown.

Tolerance during inhalation of organic solvents

Inhalation of several different halogenated solvents stimulated motor activity in mice. During prolonged exposure acute tolerance developed. The development of tolerance depended both on the schedule of exposure, and on the solvent. Exposure to trichloroethylene induced both stimulation and tolerance while the same degree of stimulation induced by 1,1,1-trichloroethane caused no tolerance. Thus the mechanisms which induce stimulation do not always initiate tolerance. Slow steady increases in the concentration of trichloroethylene could be maintained for several hours without any stimulation of motor activity. At the end of such exposures concentrations were reached which, if applied directly, would have induced considerable stimulation. Thus tolerance may develop without motor stimulation. Inhalation of ethanol also stimulated motor activity initially. During constant exposure the stimulation was followed by a considerable reduction in motor activity. This resulted in a hypoactive period, which in turn was followed by a second increase in motor activity, indicating the existence of not only two but several counteracting mechanisms. Development of metabolites with sedative effects counteracting the stimulating effect of the pure solvents seems to be one explanation for the results.

cDNA sequence of human class III alcohol dehydrogenase

A human placental cDNA library was screened using oligonucleotide probes based on the peptide sequence of the human class III alcohol dehydrogenase. An incomplete cDNA clone covering most of the coding sequence of class III alcohol dehydrogenase was isolated from a human placental cDNA library. This was subsequently used as a probe to obtain a full-length clone from a human testicular library. The cDNA sequence codes for a protein that is identical to the enzyme purified from human liver. Southern analysis of human genomic DNA suggests that it may contain more than a single copy per haploid genome.

Characteristics of mammalian class III alcohol dehydrogenases, an enzyme less variable than the traditional liver enzyme of class I

Class III alcohol dehydrogenase, whose activity toward ethanol is negligible, has defined, specific properties and is not just a "variant" of the class I protein, the traditional liver enzyme. The primary structure of the horse class III protein has now been determined, and this allows the comparison of alcohol dehydrogenases from human, horse, and rat for both classes III and I, providing identical triads for both these enzyme types. Many consistent differences between the classes separate the two forms as distinct enzymes with characteristic properties. The mammalian class III enzymes are much less variable in structure than the corresponding typical liver enzymes of class I: there are 35 versus 84 positional differences in these identical three-species sets. The class III and class I subunits contain four versus two tryptophan residues, respectively. This makes the differences in absorbance at 280 nm a characteristic property. There are also 4-6 fewer positive charges in the class III enzymes accounting for their electrophoretic differences. The substrate binding site of class III differs from that of class I by replacements at positions that form the hydrophobic barrel typical for this site. In class III, two to four of these positions contain residues with polar or even charged side chains (positions 57 and 93 in all species, plus positions 116 in the horse and 140 in the human and the horse), while corresponding intraclass variation is small. All these structural features correlate with functional characteristics and suggest that the enzyme classes serve different roles. In addition, the replacements between these triad sets illustrate further general properties of the two mammalian alcohol dehydrogenase classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of mechanism-based reversible inhibitors on the metal environment of cobalt(II)carboxypeptidase A: an electronic spectral study

Electronic absorption, circular dichroic (CD), and magnetic circular dichroic (MCD) spectra have been determined for complexes of cobalt(II)-substituted carboxypeptidase A and five reversible inhibitors. Three of the inhibitors, N-(1-carboxy-5-butyloxycarbonylaminopentyl)-L-phenylalanine, (I); (R,S)-2-benzyl-4-oxobutanoic acid, (III); and 2-benzyl-4-oxo-5,5,5-trifluoropentanoic acid, (IV) are mechanism-based inhibitors. Another, N-(1-carboxy-5-carbobenzoxyaminopentyl)-glycyl-L-phenylalanine, (II), is a tight binding, slowly hydrolyzed substrate. The fifth, phosphoramidon, (V), is a mechanism-based inhibitor of thermolysin, and may also bind to carboxypeptidase in a mechanism-based mode. The absorption and CD spectra of the enzyme-inhibitor complexes all differ from the spectrum of the free enzyme and from each other. The MCD spectra indicate that the tetrahedral coordination geometry of cobalt, which is distorted in the free enzyme, is also distorted in the inhibitor complexes, although to various degrees. The complexes of I and III are spectrally similar despite being structurally dissimilar, and that of IV, whose structure resembles III, is spectrally distinct, indicating that I and III, but not IV, may perturb the metal in nearly the same way. The absorption spectrum of IV is identical to that, at high pH, of Co(II)carboxypeptidase in which Glu-270 has been modified by a carbodiimide reagent, possibly pointing to a common perturbation of this residue. The absorption and CD spectra of II are similar to those of the catalytic intermediate that precedes the rate-limiting step in peptide hydrolysis [D. S. Auld, A. Galdes, K. F. Geoghegan, B. Holmquist, R. Martinelli, and B. L. Vallee, Proc. Natl. Acad. Sci. USA 81, 4675-4681 (1984)]. Since II is a substrate, the steady-state bound species that it generates may therefore be a true productive intermediate rather than a nonproductive mimic of an intermediate. The spectra of the complexes with II and V differ considerably despite structural similarities. The negative CD ellipticity of the free enzyme is reversed in sign in the presence of V, a phenomenon previously observed with complexes of Co(II)carboxypeptidase and dipeptides. This resemblance may result from a similar interaction of cobalt with the phosphoramidate group of phosphoramidon and the N-terminal amine of dipeptides. The spectra of reversible, mechanism-based inhibitors permit general structural predictions about true intermediates but require caution when used for assigning precise conformation and ligands of bound catalytic species.

An angiotensin converting enzyme inhibitor is a tight-binding slow substrate of carboxypeptidase A

Carboxypeptidase A-catalyzed hydrolysis of peptides and depsipeptides is competitively inhibited by N-(1-carboxy-5-t-butyloxycarbonylaminopentyl)-L-phenylalanine (Boc-CA-Phe, Ki = 1.3 microM) and the angiotensin converting enzyme inhibitor, N-(1-carboxy-5-carbobenzoxyaminopentyl)-glycyl-L-phenylalanine (Z-CA-Gly-Phe, Ki = 4.5 microM). The latter compound is actually a slow substrate of carboxypeptidase. Indirect observation of inhibitor binding by stopped-flow measurement of radiationless energy transfer between carboxypeptidase tryptophans and dansylated substrates reveals slow binding for both compounds. The visible absorption spectrum of the complex of cobalt(II)-substituted carboxypeptidase and Z-CA-Gly-Phe, which differs from the corresponding spectrum of the Boc-CA-Phe complex, is remarkable in its resemblance to the spectrum of the complex between Co(II)carboxypeptidase and a transient intermediate previously observed during hydrolysis of peptide substrates. The spectrum slowly changes to that of the free enzyme indicating hydrolysis. Chromatographic quantitation of substrate and products confirms that carboxypeptidase converts Z-CA-Gly-Phe to Z-CA-Gly and L-Phe with an apparent kcat of 0.02 s-1. Absorption spectroscopy indicates that the Z-CA-Gly-Phe-Co(II)carboxypeptidase spectrum is not that of bound products. Moreover, spectral titrations indicate that the products (both with spectral Ki values of about 3 mM), as well as D-Phe, compete for the same site on the enzyme.

Fluorometric assays for isozymes of human alcohol dehydrogenase

Two new fluorogenic substrates for human alcohol dehydrogenase (ADH), 4-methoxy-1-naphthaldehyde (IA) and 6-methoxy-2-napthaldehyde (IIA), are described. The 2-naphthaldehyde derivative fluoresces in aqueous media with a quantum yield of 0.22 with an emission maximum at 450 nm, but the 1-naphthaldehyde shows only weak fluorescence. The corresponding alcohol reduction products, 4-methoxy-1-naphthalenemethanol (IB) and 6-methoxy-2-naphthalenemethanol (IIB), exhibit fluorescence in the near uv region with quantum yields of 0.36 and 0.26, respectively. The Km values for the individual homogenous class I ADH isozymes, with the above naphthaldehydes as substrates, range from 0.35 to 11.5 microM. The kappa cat values range from 70 to 610 min-1 and are thus comparable to those for the best ADH substrates. Except for the beta 1 beta 1 isozyme, IA is the preferred substrate for class I ADH isozymes while IIA is rapidly reduced by class II (pi-ADH). The sensitivity and specificity of the enzymatic assay with IA as substrate are demonstrated and provide the basis for the determination of class I ADH activity in human serum.

Characterization of the inhibitor complexes of cobalt carboxypeptidase A by electron paramagnetic resonance spectroscopy

The metal coordination sphere of cobalt-substituted carboxypeptidase A and its complexes with inhibitors has been characterized by X-band electron paramagnetic resonance (EPR) spectroscopy. The temperature dependence of the EPR spectrum of cobalt carboxypeptidase and the g anisotropy are consistent with a distorted tetrahedral geometry for the cobalt ion. Complexes with L-phenylalanine, a competitive inhibitor of peptide hydrolysis, as well as other hydrophobic L-amino acids all exhibit very similar EPR spectra described by three g values that differ only slightly from that of the cobalt enzyme alone. In contrast, the EPR spectra observed for the cobalt enzyme complexes with 2-(mercaptoacetyl)-D-Phe, L-benzylsuccinate, and L-beta-phenyllactate all indicate an approximately axial symmetry of the cobalt atom in a moderately distorted tetrahedral metal environment. Phenylacetate, beta-phenylpropionate, and indole-3-acetate, which exhibit mixed modes of inhibition, yield EPR spectra indicative of multiple binding modes. The EPR spectrum of the putative 2:1 inhibitor to enzyme complex is more perturbed than that of the 1:1 complex. For beta-phenylpropionate, partially resolved hyperfine coupling (122 x 10(-4) cm-1) is observed on the g = 5.99 resonance, possibly indicating a stronger metal interaction for this binding mode. The structural basis for the observed EPR spectral perturbations is discussed with reference to the existing crystallographic kinetic and electronic absorption, nuclear magnetic resonance, and magnetic circular dichroic data.

A human liver alcohol dehydrogenase enzyme-linked immunosorbent assay method specific for class I, II, and III isozymes

A sensitive and convenient method for the quantitative measurement of human alcohol dehydrogenase (ADH) isozymes based on enzyme-linked immunosorbent assay has been devised. The procedure was optimized with respect to antigen coating density, antiserum dilution, and incubation times with rabbit antisera raised against beta 1 beta 1-ADH to achieve a limit of sensitivity of 1 ng/ml for this isozyme when purified. Using the optimal conditions established, quantitative measurement of alpha beta 1, alpha gamma 1, beta 1 gamma 1, pi, and chi-ADH were obtained with antisera raised in rabbits toward these individual isozymes. The incorporation into the procedure of thimerosal (ethyl(4-mercaptobenzoato-S)mercury) or other sulfhydryl specific reagents improved the soluble phase antiserum avidity for all ADH isozymes, thereby increasing the sensitivity. Thimerosal is an absolute requirement for chi-ADH antigen-antibody binding. The polyclonal rabbit antisera elicited by the individual isozymes of the three classes of ADH exhibit a high degree of isozyme class specificity. Cross-reactivity of the antibodies with the beta 1 beta 1, alpha gamma 1, alpha gamma 2, alpha beta 1, beta 1 gamma 1, beta 1 gamma 2, pi and chi isozymes were evaluated. Antisera against the class I isozymes beta 1 beta 1 and beta 1 gamma 1 cross-react with all class I isozymes and with pi-ADH. Antibodies against pi and chi-ADH are selective and specific only for their respective antigens. Neither one cross-reacts with any class I isozyme. Conformational effects resulting from subunit interactions likely account for differences in cross-immunoreactivity between the closely homologous class I isozymes.

3 beta-Hydroxy-5 beta-steroid dehydrogenase activity of human liver alcohol dehydrogenase is specific to gamma-subunits

Human liver alcohol dehydrogenase [alcohol:NAD+ oxidoreductase, EC 1.1.1.1 (ADH)] catalyzes the stereospecific oxidation of different 3 beta-hydroxy-5 beta-steroids with ranges of Km from 46 to 320 microM and values of kcat from 7.0 to 72 min-1, pH 8.5. Only the class I isozymes containing gamma-subunits, gamma 1 gamma 1, alpha gamma 1, beta 1 gamma 1, gamma 2 gamma 2, and beta 1 gamma 2, catalyze oxidation of these steroids with kcat/Km ratios 4-10-fold greater than those for ethanol. In marked contrast, class I alpha alpha, alpha beta 1, and beta 1 beta 1, class II, and class III isozymes do not oxidize 3 beta-hydroxy-5 beta-steroids though they readily oxidize ethanol. 1,10-Phenanthroline and 4-methylpyrazole competitively inhibit both alcohol dehydrogenase catalyzed ethanol and 3 beta-hydroxy-5 beta-steroid oxidation demonstrating that the catalysis of both types of substrates occurs at the same active site. The gamma-subunit-catalyzed oxidation of 3 beta-hydroxy-5 beta-steroids is the most specific catalytic function described thus far for any human liver alcohol dehydrogenase isozyme: there is no other isozyme that catalyzes this reaction. Testosterone, an allosteric inhibitor of ethanol oxidation specific for gamma-subunit-containing human liver ADH isozymes [Mårdh, G., Falchuk, K. H., Auld, D. S., & Vallee, B. L. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 2836-2840], also noncompetitively inhibits gamma-subunit-catalyzed sterol oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of the carboxypeptidase responsible for the post-synthetic modification of creatine kinase in human serum

The enzyme responsible for the post-translational modification of creatine kinase-MM isoenzyme was purified from human plasma. The enzymatic activity of this enzyme (modifying protein) on the synthetic substrates hippuryl-L-arginine, hippuryl-L-lysine, 3-(2-furylacryloyl)-L-arginine and 3-(2-furylacryloyl)-L-alanyl-L-lysine and the ratio of activities on these substrates are in good agreement with the enzymatic activity of the human serum carboxypeptidase N. The effect of metal ions, chelating agents, proteolytic inhibitors and carboxypeptidase N inhibitor could not differentiate the modifying protein from human serum carboxypeptidase N. Affinity chromatography on Concanavalin-A-Sepharose demonstrated the glycoprotein nature of the modifying protein. The difference in molecular weight observed between modifying protein and carboxypeptidase N can be explained by known instability characteristics and the influence of proteolytic enzymes during purification. Double immunodiffusion analysis with purified antiserum to human carboxypeptidase N confirmed the identity of the modifying protein and carboxypeptidase N.

Class III human liver alcohol dehydrogenase: a novel structural type equidistantly related to the class I and class II enzymes

The primary structure of class III alcohol dehydrogenase (dimeric with chi subunits) from human liver has been determined by peptide analyses. The protein chain is a clearly distinct type of subunit distantly related to those of both human class I and class II alcohol dehydrogenases (with alpha, beta, gamma, and pi subunits, respectively). Disregarding a few gaps, residue differences in the chi protein chain with respect to beta 1 and pi occur at 139 and 140 positions, respectively. Compared to class I, the 373-residue chi structure has an extra residue, Cys after position 60, and two missing ones, the first two residues relative to class I, although the N-terminus is acetylated like that for those enzymes. The chi subunit contains two more tryptophan residues than the class I subunits, accounting for the increased absorbance at 280 nm. There are also four additional acidic and two fewer basic side chains than in the class I beta structure, compatible with the markedly different electrophoretic mobility of the class III enzyme. Residue differences between class III and the other classes occur with nearly equal frequency in the coenzyme-binding and catalytic domains. The similarity in the number of exchanges relative to that of the enzymes of the other two classes supports conclusions that the three classes of alcohol dehydrogenase reflect stages in the development of separate enzymes with distinct functional roles. In spite of the many exchanges, the residues critical to basic functional properties are either completely unchanged--all zinc ligands and space-restricted Gly residues--or partly unchanged--residues at the coenzyme-binding pocket.(ABSTRACT TRUNCATED AT 250 WORDS)

Electronic spectroscopy of cobalt angiotensin converting enzyme and its inhibitor complexes

Zinc, the catalytically essential metal of angiotensin converting enzyme (ACE), has been replaced by cobalt(II) to give an active, chromophoric enzyme that is spectroscopically responsive to inhibitor binding. Visible absorption spectroscopy and magnetic circular dichroic spectropolarimetry have been used to characterize the catalytic metal binding site in both the cobalt enzyme and in several enzyme-inhibitor complexes. The visible absorption spectrum of cobalt ACE exhibits a single broad maximum (525 nm) of relatively low absorptivity (epsilon = 75 M-1 cm-1). In contrast, the spectra of enzyme-inhibitor complexes display more clearly defined maxima at longer wavelengths (525-637 nm) and of markedly higher absorptivities (130-560 M-1 cm-1). The large spectral response indicates that changes in the cobalt ion coordination sphere occur on inhibitor binding. Magnetic circular dichroic spectropolarimetry has shown that the metal coordination geometry in the inhibitor complexes is tetrahedral and of higher symmetry than in cobalt ACE alone. The presence of sulfur----cobalt charge-transfer bands in both the visible absorption and magnetic circular dichroic spectra of the cobalt ACE-Captopril complex confirm direct ligation of the thiol group of the inhibitor to the active-site metal.

Acetylated N-terminal structures of class III alcohol dehydrogenases. Differences among the three enzyme classes

The protein chains of mammalian alcohol dehydrogenases typically lack free alpha-amino groups. The blocked N-terminal regions of the class III type of the rat (ADH-2), human (chi chi) and horse enzymes were isolated by digestions with proteases, and characterized by mass-spectrometry supplemented with chemical analysis of the peptides and their redigestion fragments. Results were confirmed by synthesis of the corresponding peptides, followed by chromatographic comparisons of the native and synthetic products. The N-terminal regions of the three class III alcohol dehydrogenase subunits are homologous but differ from the class I and II enzymes in both the exact start position and the amino acid sequence, which suggests that different N-terminal structures are typical for each of the three classes.

A simple device for automated spectrophotometric kinetics using a diode array spectrophotometer

In this report we describe an automated system that rapidly and automatically mixes reagents and records results, such as spectrophotometric changes. It employs a commercial diode array spectrophotometer and a novel dilution chamber in a flow stream that allows repetitive spectrophotometric rate measurements at accurately measured incremental substrate concentrations. When applied to enzyme kinetic studies, initial velocities at 15 different substrate or inhibitor concentrations, or pH values, can be recorded in a few minutes with high reproducibility, i.e., standard deviations less than 1%, and high sensitivity. Reactions occur in an 8-microliters flow cell and the reagent consumption is minimal. The concentration of incrementally diluted reagent in the cell is measured directly by means of an indicator dye added to the substrate. Michaelis-Menten parameters, inhibition constants, and pH profiles are determined for several enzymes including dehydrogenases producing NADH, a kinase requiring a coupled assay, and a hydrolase, carboxypeptidase A, in a reaction that produces a small decrease in absorbance.

Structure of the class II enzyme of human liver alcohol dehydrogenase: combined cDNA and protein sequence determination of the pi subunit

The class II enzyme of human liver alcohol dehydrogenase was isolated, carboxymethylated, and cleaved with CNBr and proteolytic enzymes. Sequence analysis of peptides established structures corresponding to the pi subunit. Two segments from the C-terminal region unique to pi were selected for synthesis of oligodeoxyribonucleotide probes to screen a human liver cDNA library constructed in plasmid pT4. Sequence analysis of two identical hybridization-positive clones with cDNA inserts of about 2000 nucleotides gave the entire coding region of the pi subunit, a 61-nucleotide 5' noncoding region and a 741-nucleotide 3' noncoding region containing four possible polyadenylation sites. Translation of the coding region yields a 391-residue polypeptide, which in all regions except the C-terminal segment corresponds to the protein structure as determined directly by peptide analysis. With the class I numbering system, the exception concerns a residue exchange at position 368, the actual C-terminus which is Phe-374 by peptide data but a 12-residue extension by cDNA data, and possibly two further residue exchanges at positions 303 and 312. The size difference might indicate the existence of posttranslational modifications of the mature protein or, in combination with the residue exchanges, the existence of polymorphism at the locus for class II subunits. The pi subunit analyzed directly results in a 379-residue polypeptide and is the only class II size thus far known to occur in the mature protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Fe-S centers in lactyl-CoA dehydratase

Lactyl-CoA dehydratase consists of two enzymes, E1 and E2, and requires catalytic quantities of ATP for activity [Kuchta, R. D., & Abeles, R. H. (1985) J. Biol. Chem. 260, 13181-13189]. In contrast to E1, which contains no Fe, E2 contains 8.20 +/- 0.04 mol of Fe/mol of E2, one of which can be removed by 1,10-phenanthroline. E2 also contains 7.33 +/- 0.68 mol of inorganic sulfur/mol of E2, indicating that at least seven of the Fe atoms are present as Fe-S clusters. E1 and E2 contain less than 0.14 mol of Cu, Co, Zn, Mn, and Ni/mol of E1 or E2. Both reduced and oxidized E1 are EPR silent over a 10,000-G scan range at 4 K, while two signals in E2 are observable at 4 K. Identical spectra were obtained with E2 containing either seven or eight Fe atoms, and both signals were only observable at T less than 30 K. Signal 1 has axial symmetry with g = 2.0232 and g = 2.0006. Signal 2 is orthorhombic with g1 = 1.982, g2 = 1.995, and g3 = 2.019. Computer simulation of these spectra with a S = 1/2 spin Hamiltonian was used to extract the g matrices. The intensity of both signals decreases when E2 is reduced with Na2S2O4. We propose that signal 1 is due to an unusual [4Fe-4S] cluster and signal 2 to a [3Fe-3/4S] cluster. Addition of either acrylyl-CoA or lactyl-CoA dramatically alters signal 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Thioamide substrate probes of metal-substrate interactions in carboxypeptidase A catalysis

Three thioamide peptides in which the oxygen atom of the scissile peptide bond is replaced by sulfur (denoted by (= S)) were synthesized and found to be good, convenient substrates for carboxypeptidase A. The thioamide bond absorbs strongly in the ultraviolet region, and enzymatic hydrolysis is monitored easily using a continuously recording spectrophotometric assay. The reaction follows Michaelis-Menten kinetics with kcat values of 68, 9.0, and 3.7 sec-1 and Km values of 0.83, 0.81, and 0.53 mM for Z-Glu-Phe(= S)-Phe, Z-Gly-Ala(= S)-Phe, and Z-Phe(= S)-Phe, respectively. Activities of the thioamides and their oxygen amide analogs were determined with a series of metal-substituted carboxypeptidases. The Cd(II), Mn(II), Co(II), and Ni(II) enzymes exhibit 30%-35%, 60%-85%, 150%-190%, and 40%-55% of the Zn(II) enzyme activity with the amide substrates; this compares with 240%-970%, 0%-15%, 340%-840%, and 30%-140% of the Zn(II) activity, respectively, with the thioamides. The activity of the Cu(II) and Hg(II) enzymes is less than 3% toward all substrates. Cadmium, a thiophilic metal, yields an enzyme which is exceedingly active with the thioamides; the kcat/Km values are 2.4-9.7-fold higher than with Zn(II) carboxypeptidase. In contrast, Mn(II), which has a relatively low affinity for sulfur, yields an enzyme with correspondingly low activity toward the thioamides. The results are consistent with a mechanism for peptide bond hydrolysis in which the metal atom interacts with the substrate carbonyl atom during catalysis.

Extracellular fluid proteins of goldfish brain: evidence for the presence of proteases and esterases

Preparations of enriched fractions of extracellular fluid (ECF) proteins from goldfish brain were found to contain protease(s) and esterase(s). The N-substituted furanacryloyl (FA) peptides FA-Phe-Gly-Gly and FA-Phe-OMe were used as model substrates for determining protease and esterase activity, respectively, in a spectrophotometric assay. Studies of the profile of substrate specificity and identification of the types of compounds that were effective as inhibitors showed that these ECF enzymes have some distinctive properties. GSH, but not GSSG, and EDTA inhibited the protease(s) without influencing the esterase(s), whereas L-1-tosylamide-2-phenylethylchloromethyl ketone blocked both protease and esterase activities of ECF. Most of the protease and esterase properties of ECF could be bound to concanavalin A-Sepharose affinity chromatographic columns in association with ependymin--a brain extracellular protein. These observations indicate that ECF may contain a metalloprotease(s) and raise the possibility that the ependymins might be a substrate for these ECF enzymes.

Hydrolysis of peptides by carboxypeptidase A: equilibrium trapping of the ES2 intermediate

The cobalt absorption and electron paramagnetic resonance (EPR) spectra of cobalt carboxypeptidase undergo unique variations on formation of catalytic peptide and ester intermediates as previously recorded in cryoenzymologic experiments employing rapid-scanning spectroscopy and cryotrapping [Geoghegan, K. F., Galdes, A., Martinelli, R. A., Holmquist, B., Auld, D.S., & Vallee, B. L. (1983) Biochemistry 22, 2255-2262]. We here describe a means of stabilizing these intermediates, which we have termed "equilibrium trapping". It allows peptide intermediates to be observed for longer periods (much greater than 1 min) at ambient as well as subzero temperatures. The reaction intermediate with the rapidly turned over peptide substrate Dns-Ala-Ala-Phe is trapped when the cobalt enzyme (greater than 10 microM) has catalyzed the attainment of chemical equilibrium between high concentrations of the hydrolysis products Dns-Ala-Ala, 10 mM, and L-phenylalanine, 50 mM, and the product of their coupling Dns-Ala-Ala-Phe. Under these conditions, Dns-Ala-Ala-Phe is present in the equilibrated substrate-product reaction mixture at a level that exceeds the one predicted on the basis of K'eq for hydrolysis of this substrate and is close to the enzyme concentration. Other pairs of peptide hydrolysis products yield similar results. Visible absorption and EPR spectra of the cobalt enzyme show that the synthesized peptide binds to the active site in the mode previously recognized as the ES2 catalytic intermediate in peptide hydrolysis. Equilibrium trapping of the ES2 intermediate allows analysis of its physicochemical properties by methods that could not be employed readily under cryoenzymological conditions, e.g., circular dichroic and magnetic circular dichroic spectra.(ABSTRACT TRUNCATED AT 250 WORDS)

A spectral study of cobalt(II)-substituted Bacillus cereus phospholipase C

The coordination sphere of both the structural and catalytic zinc ions of Bacillus cereus phospholipase C has been probed by substitution of cobalt(II) for zinc and investigation of the resultant derivatives by a variety of spectroscopic techniques. The electronic absorption, circular dichroic, magnetic circular dichroic, and electron paramagnetic resonance spectra were found to be strikingly similar when cobalt(II) was substituted into either site and are consistent with a distorted octahedral environment for the metal ion in both sites. Octahedral coordination appears comparatively rare in zinc metalloenzymes but has been suggested for glyoxalase I [Sellin, S., Eriksson, L. E. G., Aronsson, A.-C., & Mannervik, B. (1983) J. Biol. Chem. 258, 2091-2093; Garcia-Iniguez, L., Powers, L., Chance, B., Sellin, S., Mannervik, B., & Mildvan, A. S. (1984) Biochemistry 23, 685-689], transcarboxylase [Fung, C.-H., Mildvan, A. S., & Leigh, J. S. (1974) Biochemistry 13, 1160-1169], and the regulatory binding site of Aeromonas aminopeptidase [Prescott, J. M., Wagner, F. W., Holmquist, B., & Vallee, B. L. (1985) Biochemistry 24, 5350-5356]. Phospholipase C is so far unique in having two such sites.

Effects of methylene chloride on body and organ weight and plasma butyrylcholinesterase activity in mice

Exposure to methylene chloride produced a time and concentration related increase in liver weight. The effect was more prominent in female mice than in male. The activity of plasma butyrylcholinesterase (BuChE) increased even more than the liver weight at corresponding exposures, but only in the males. Fatty infiltration was noticeable after exposure to 75 p.p.m. and was more prominent in the females than in the males. Thirty to 60 days of continuous exposure were required to reach stable maxima. Intermittent exposure was less effective than continuous exposure in producing the effects. Most effects were fully reversible after exposure for both 30 and 90 days if the animals were transferred to a solvent-free environment. However, after exposure for 90 days, BuChE activity in the males did not return to normal within 30 days but after 90 and 120 days free from exposure only slight if any effects on BuChE activity remained.

cDNA and protein structure for the alpha subunit of human liver alcohol dehydrogenase

Two cDNA clones for human liver alcohol dehydrogenase (ADH) were identified, together covering 1450 nucleotides that contain the cDNA sequence of the ADH1 locus and include a coding region of 1122 nucleotides for the alpha subunit of the enzyme. In parallel, direct peptide analyses of the carboxymethylated protein also established most of the amino acid sequence. Nucleotide and peptide data were in complete agreement and show exchanges at 24 positions in the alpha relative to the beta subunit. One of the cDNA clones had a 139-nucleotide internal deletion at a position of possible interest in relation to mRNA processing, ancestral connections, or DNA replication. The structure of the alpha subunit is homologous to that of the beta and gamma subunits but has many exchanges, also of functionally important residues, explaining the different enzymatic properties. In total, 35 of 374 amino acid residues differ between the class I isozymes, and the substitutions add an extra SH group in the alpha subunit. Only in the beta-pleated sheet region of the coenzyme-binding domain is almost complete lack of substitutions noted, illustrating the importance of this region. In contrast, the active site region is far less conserved. However, similar exchanges of functional significance have also been found in distantly related alcohol and polyol dehydrogenases.

Kininase II of human seminal fluid: kinetics and inhibition

The activity of kininase II in crude human sperm was measured continuously by measuring the hydrolysis of a blocked tripeptide 3-(2-furylacryloyl)-L- phenylalanyl-glycyl-glycine (1 mmol/l). Mean seminal plasma activity was 335 +/- 61 U/g protein; the Km was 0.7 mmol/l; pH optimum was 8.8 in a 50 mmol/l HEPES buffer and the chloride optimum was 300 mmol/l. This male genital tract enzyme is inhibited by several kininase II inhibitors. Captopril (SQ 14225) showed IC50 = 1.6 X 10(-8) mol/l, with a competitive pattern (Ki = 7.3 X 10(-9)). 3-(Mercaptomethyl)-oxo-piperidineacetic acid showed the same kind of inhibition with an IC50 = 1.8 X 10(-6) mol/l (Ki = 6.8 X 10(-7) mol/l). Enalapril diacid was the most potent inhibitor and had an IC50 of 4.1 X 10(-9) mol/l and showed a mixed competitive and non-competitive inhibition (Ki = 10(-9) mol/Ki' = 9.5 X 10(-10) mol/l). These in vitro inhibition data suggest that, in vivo, such drugs may effect the function of kininase II in the male reproductive system. The observed 50% inhibition constants are comparable to those observed in lung enzyme suggesting similar kinetic properties.

Cardiovascular complications of estrogen therapy for nondisseminated prostatic carcinoma. A preliminary report from a randomized multicenter study

In a prospective multicenter study, 244 men with highly or moderately differentiated prostatic cancer in stage I, II or III (VACURG) were consecutively randomized to three groups of treatment: Group A (77 patients) received polyestradiol phosphate (Estradurin, Leo) 80 mg i.m. every fourth week + ethinyl estradiol (Etivex, Leo) 150 micrograms daily, group B (72 patients) estramustine phosphate (Estracyt, Leo) 280 mg twice daily, and group C (76 patients) no therapy. Only men without current or previous other malignancy and without cardiovascular disease were admitted to the study. After 4 1/2 years 125 of the 244 patients had left the study, 9 because of cancer progression (stage IV, VACURG). The most serious complications were cardiovascular, including ischemic heart disease, cardiac decompensation, cerebral ischemia and venous thromboembolism, which occurred in 24 patients from group A and 9 from group B as compared to only one patient in group C. The subgroup superficial or deep venous thrombosis comprised 11 group A and 2 group B patients. Estrogens (E + e) offered as palliative treatment to patients with non-generalized prostatic carcinoma is burdened with a high incidence of serious cardiovascular complications.

chi-ADH is the sole alcohol dehydrogenase isozyme of mammalian brains: implications and inferences

Class III (chi) is the only alcohol dehydrogenase (ADH) in human, equine, bovine, simian, canine, and rodent brain and is the first to be identified, purified, and characterized from the brain of humans or other vertebrates. Like the corresponding isozymes from human placenta and liver, the chi-ADH isozymes purified from mammalian brain are neither inhibited by nor do they bind to immobilized pyrazole, and they oxidize ethanol only very poorly (Km greater than 2.5 M). Indeed, it would be incorrect to classify them as "ethanol dehydrogenases." They contain 4 g.atom of zinc/mol, bind 2 moles of NAD, and readily oxidize long-chain aliphatic and aromatic primary alcohols. These findings appear to exclude the possibilities that ADH protects the brain of these vertebrates against ethanol or its metabolic products and that the brain can generate energy for cerebral function from ADH-monitored ethanol metabolism. Thus chi-ADH must serve a totally different but as yet unknown role. The failure to detect any ethanol dehydrogenase activity in brain creates an intellectual dilemma only if it is assumed that such an enzyme has evolved and developed as a protective mechanism for ethanol detoxification in that organ, as has been assumed. Tissue and substrate specificities of ADH isozymes are likely to give new insight regarding their physiological roles.

Effects of solvent exposure on testosterone levels and butyrylcholinesterase activity in mice

In female and male mice the effect of exposure to trichloroethylene (TCE) seen at the lowest concentration is an increase in liver weight. The activity of plasma butyrylcholinesterase (BuChE) increases even more than the liver weight at corresponding concentrations, but only in the males. Depletion of testosterone through castration or destruction of the pituitary gland or hypothalamus, are the only other ways to experimentally induce corresponding increases in BuChE. Plasma BuChE activity increase was found to be a common reaction after exposure to TCE, perchloroethylene, chloroform, methylene chloride and carbon tetrachloride and also after exposure to ethanol. Other solvents such as toluene, xylene, benzene and 1,1,1-trichloroethane had little or no effect on BuChE activity. Normal and castrated male mice were continuously exposed for one month to 150 p.p.m. TCE. The increase in BuChE activity after the exposure was of the same magnitude as the increase seen after castration. BuChE activity in castrated males was not further increased by TCE exposure. Administration of testosterone with osmotic minipumps for 13 days almost restored the normal testosterone and BuChE levels in castrates. The effect of TCE exposure on BuChE activity in these animals was the same as on normal males. Testosterone levels were not influenced by the TCE exposure in normal males or in castrates given testosterone. No sex hormone binding globulins (SHBG) could be detected in the mice. BuChE activity changes induced through solvent exposure are therefore neither directly nor indirectly (through SHBG) due to effects on testosterone. The results from these animal experiments do not support the epidemiological findings of decreased testosterone levels in humans exposed to solvents.

Spectral and kinetic studies of metal-substituted Aeromonas aminopeptidase: nonidentical, interacting metal-binding sites

Apoenzyme prepared by removal of the 2 mol of Zn2+/mol from Aeromonas aminopeptidase is inactive. Addition of Zn2+ reactivates it completely, and reconstitution with Co2+, Ni2+, or Cu2+ results in a 5.0-, 9.8-, and 10-fold more active enzyme than native aminopeptidase, respectively. Equilibrium dialysis and spectral titration experiments with Co2+ confirm the stoichiometry of 2 mol of metal/mol. The addition of only 1 mol of metal/mol completely restores activity characteristic of the particular metal. Interaction between the two sites, however, causes hyperactivation; thus, addition of 1 mol of Zn2+/mol subsequent to 1 mol of Co2+, Ni2+, or Cu2+ per mole increases activity 3.2-, 42-, or 59-fold, respectively. The cobalt absorption spectrum has a peak of 527 nm with a molar absorptivity of 53 M-1 cm-1 for 1 mol of cobalt/mol, which increases to 82 M-1 cm-1 for a second cobalt atom and is unchanged by further addition of Co2+. Circular dichroic (CD) and magnetic CD spectra indicate that the first Co2+ binding site is tetrahedral-like and that the second is octahedral-like. Stoichiometric quantities of 1-butylboronic acid, a transition-state analogue inhibitor of the enzyme [Baker, J. O., & Prescott, J. M. (1983) Biochemistry 22, 5322], profoundly affects absorption, CD, and MCD spectra, but n-valeramide, a substrate analogue inhibitor, has no effect. These findings suggest that the tetrahedral-like site is catalytic and the other octahedral-like site is regulatory or structural.

Structural relationships among class I isozymes of human liver alcohol dehydrogenase

The alpha subunit of human liver alcohol dehydrogenase has been submitted to structural analysis. Together with earlier work on the beta and gamma subunits, the results allow conclusions on the relationship of all known forms of the class I type of the enzyme. Two segments of the alpha subunit were determined; one was also reinvestigated in the beta and gamma subunits. The results establish 11 residue replacements among class I subunits in the segments analyzed and show that the alpha, beta, and gamma protein chains each are structurally distinct in the active site regions, where replacements affect positions influencing coenzyme binding (position 47; Gly in alpha, Arg in beta and gamma) and substrate specificity (position 48; Thr in alpha and beta, Ser in gamma). Residue 128, previously not detected in beta and gamma subunits, corresponds to a position of another isozyme difference (Arg in beta and gamma, Ser in alpha). The many amino acid replacements in alcohol dehydrogenases even at their active sites illustrate that in judgements of enzyme functions absolute importance of single residues should not be overemphasized. Available data suggest that alpha and gamma are the more dissimilar forms within the family of the three class I subunits that have resulted from two gene duplications. The class distinction of alcohol dehydrogenases previously suggested from enzymatic, electrophoretic, and immunological properties therefore also holds true in relation to their structures.

Narcan inhibition of human liver alcohol dehydrogenase

Narcan, the pharmaceutical agent for the administration of naloxone, has been reported to antagonize ethanol intoxication. In addition to naloxone, Narcan contains the antioxidant esters methyl- and propylparaben. Pure naloxone and these two esters were examined for their capacity to inhibit ethanol oxidation by purified isozymes of human liver alcohol dehydrogenase (ADH). Naloxone (400 micromolar) fails completely to inactivate any of the three ADH isozyme classes. In contrast, methyl- and propylparaben, and some related esters, competitively inhibit the oxidation of ethanol and reduction of acetaldehyde by all isozymes examined. The reported effects of Narcan on ethanol-intoxicated animals or cells cannot be attributed to the action of naloxone.

Effects of organic solvents on motor activity in mice

Groups of male mice were exposed via inhalation to methylene chloride, perchloroethylene, toluene, trichloroethylene or 1,1,1-trichloroethane. The exposures were started at 2300 h. Generation of vapor was stopped after 1 h. Motor activity of the animals during the exposures was measured with a Doppler radar. Several concentrations of each solvent were tested. Concentrations could be found for all solvents at which they initially increased the motor activity. When the generation of vapor was terminated and the concentration started to decline, a new phase of changes in motor activity was induced. At this phase, motor activity was in most cases influence in the opposite direction to that at the beginning of the exposure. Trichloroethylene concentrations could be found which gave no increase in activity at the start of exposure but a prominent decrease at termination. The lowest concentration at which effects could be seen was different for the different solvents. Perchloroethylene was more and 1,1,1-trichloroethane less potent than the other solvents in inducing motor activity. The time pattern of the motor activity alterations was specific for each solvent. Both the concentration and the rate of the concentration increase were responsible for the effects on motor activity. The differences between the solvents probably reflect differences in their site of action, their distribution and their biotransformation.

Physical and enzymatic properties of a class II alcohol dehydrogenase isozyme of human liver: pi-ADH

Homogeneous class II alcohol dehydrogenase (pi-ADH) has been isolated from human liver homogenates by chromatography on DE-52 cellulose, 4-[3-[N-(6-amino-caproyl)amino]propyl]pyrazole-Sepharose, SP-Sephadex C-50, and agarose-hexane-AMP, yielding an enzyme that has a significantly higher specific activity and is markedly more stable than that isolated by an earlier procedure. pi-ADH is composed of two identical 40 000-dalton subunits, contains 4 mol of zinc/dimer, and is readily inhibited by metal-chelating agents. The purified enzyme binds two molecules of coenzyme per dimer, exhibits an absorption maximum at 280 nm, epsilon 280 = 57 000, and exhibits an isoelectric point of 8.6. The class II isozyme catalyzes the oxidation of a variety of alcohols with Km values ranging from 7 microM to 560 mM and with kcat values from 32 min-1 to 600 min-1 and demonstrates a preference for hydrophobic substrates. The kcat/Km ratio for ethanol oxidation exhibits a pH maximum at 10.4.

Human liver alcohol dehydrogenase. 1. The primary structure of the beta 1 beta 1 isoenzyme

Determination of the amino acid sequence of the beta 1 subunit from the class I (pyrazole-sensitive) human liver alcohol dehydrogenase isoenzyme beta 1 beta 1 revealed a 373-residue structure differing at 48 positions (including a gap) from that of the subunit of the well studied horse liver alcohol dehydrogenase EE isoenzyme. The structure deduced is compatible with known differences in composition, ultraviolet absorbance, electrophoretic mobility and catalytic properties between the horse and human enzymes. All zinc-liganding residues of the horse E subunit are strictly conserved in the human beta 1 subunit, despite an earlier report of a mutation involving Cys-46. This residue therefore remains conserved in all known alcohol dehydrogenase structures. However, the total cysteine content of the beta 1 structure is raised from 14 in the subunit of the horse enzyme to 15 by a Tyr----Cys exchange. Most exchanges are on the surface of the molecule and of a well conserved nature. Substitutions close to the catalytic centre are of interest to explain the altered substrate specificity and different catalytic activity of the beta 1 homodimer. Functionally, a Ser----Thr exchange at position 48 appears to be of special importance, since Thr-48 in beta 1 instead of Ser-48 in the horse enzyme can restrict available space. Four other substitutions also line the active-site pocket, and appear to constitute partly compensated exchanges.

Cryospectrokinetic characterization of intermediates in biochemical reactions: carboxypeptidase A

Cryospectrokinetic studies provide concurrent structural, kinetic, and chemical data on short-lived intermediates in the course of the interactions of enzymes with their substrates and of other, similar pairs of biomolecules. Subzero temperatures extend the lifetimes of these intermediates and, combined with rapid-mixing and rapid-scanning instrumentation, allow simultaneous measurement of both their physical-chemical and kinetic characteristics. For carboxypeptidase A, the spectra of a chromophoric, enzymatically functional cobalt atom at the active site signal the structure of the coordination complex during catalysis, while radiationless energy transfer between enzyme tryptophans and the fluorescent dansyl blocking group of rapidly hydrolyzed peptide and ester substrates provides the basis for measurement of the rates of formation and breakdown of intermediates. Subzero radiationless energy transfer kinetic studies of the zinc and cobalt enzymes disclose two intermediates in the hydrolysis of both peptides and esters and furnish all the rate and equilibrium constants for the reaction scheme E + S in equilibrium ES1 in equilibrium ES2----E + P. The chemical and kinetic data indicate that neither of these is an acylenzyme intermediate. Both absorption and EPR spectra of the ES2 reaction intermediates consistently demonstrate the formation of transient metal complexes, differences between the effects induced by peptides and esters, and strong similarities between those induced by all peptides on the one hand and all esters on the other. The marked alterations of the cobalt spectra likely reflect the coordination of a substrate carboxyl and/or carbonyl group to the metal at a critical step in the course of catalysis. The cryospectrokinetic approach developed here in the mechanistic study of this metalloenzyme is applicable to the examination of transients of biochemical reactions in general. It will allow molecular characterization of previously elusive intermediates and greatly magnify the range of mechanistic questions that can be answered.

Physical and enzymatic properties of a class III isozyme of human liver alcohol dehydrogenase: chi-ADH

chi-Alcohol dehydrogenase (chi-ADH), a class III isozyme characterized by its anodic electrophoretic mobility and lack of inhibition by 4-methylpyrazole, has been isolated from human liver and purified to homogeneity in a reducing medium. chi-ADH resembles other human liver ADH isozymes of classes I and II with respect to its molecular weight, dimeric structure, stoichiometry of zinc and NADH binding, and pH optima for the oxidation of alcohols. This homodimer exhibits subtle differences in its absorption spectrum and amino acid composition relative to those of other human isozymes but differs markedly from their specificity toward alcohols and aldehydes. chi-ADH oxidizes ethanol very poorly. The reaction is bimolecular, and an apparent Km cannot be discerned up to 2.3 M ethanol. The enzyme is inactive toward methanol, ethylene glycol, digitoxigenin, digoxigenin, and gitoxigenin , but alcohols with carbon chain lengths greater than four are oxidized rapidly with Km values decreasing with increasing carbon chain length. Taken jointly, the composition, structure, and enzymatic properties of the ADH isozymes purified and studied so far strongly imply that their metabolic roles, yet to be discovered, will give a new perspective to ethanol metabolism and pathology.

Perchloroethylene: effects on body and organ weights and plasma butyrylcholinesterase activity in mice

The effects of continuous and intermittent inhalation of perchloroethylene (PCE) on plasma butyrylcholinesterase (BuChE) activity, organ weights, liver morphology and motor activity in mice (strain NMRI) were tested. PCE exposure increased plasma BuChE activity in a time- and concentration dependent manner in both sexes. The increase was statistically significant at 37 p.p.m. in animals continuously exposed for 30 days. BuChE increased approximately 1.5 times in females and 2.5 times in males after 120 days exposure to 150 p.p.m. After rehabilitation of animals exposed for 30 days to 150 p.p.m., BuChE levels returned to normal. Liver weight also increased in a time and concentration dependent manner. Both sexes exhibited significant liver enlargement at 9 p.p.m. The increase was about 2.3 in females and 1.9 in males after continuous exposure to 150 p.p.m. for 120 days. After rehabilitation (120 days) of animals exposed to 150 p.p.m. for 30 days, a 10% increase still remained. A decrease in body weight gain was seen in both sexes after exposure to concentrations above 75 p.p.m. Female kidney weight was slightly increased. No clear effect on spleen weight could be detected. When the same time-weighted average concentration was used, intermittent exposure for 30 days had similar effects on liver weight and BuChE activity as continuous exposure, even when exposures lasted for only one hour per day. Liver cell morphology was changed after PCE exposure. The alterations could be observed already at 9 p.p.m. but disappeared after rehabilitation.

Pitfalls in the interpretation of long-term inhalation experiments

Age- and weight-matched groups of mice were enclosed in airtight chambers and exposed to clean, filtered air for 1 month. At the end of the exposure period, body, liver and spleen weights and plasma butyrylcholinesterase (BuChE) activity were measured. More than twice as many significant differences in these parameters occurred compared with the expected results if only random differences existed between the groups. Thus, isolation of animal groups for extended periods of time in inhalation experiments alone may lead to differences in various biological parameters. When testing the effects of unknown substances such differences may be mistaken for reactions to the test agent, which actually may have no effect.

Affinity chromatographic purification of angiotensin converting enzyme

The compounds N-[1 (S)-carboxy-5-amino-pentyl]-L-phenylalanylglycine and N-[1 (S)-carboxy-5-aminopentyl]-DL-alanyl-L-proline were synthesized and explored as potential ligands for the affinity chromatography of angiotensin converting enzyme (dipeptidyl carboxypeptidase, EC 3.4.15.1) (ACE), a membrane-bound zinc metalloprotease. The N-alkylated Ala-Pro derivative has an apparent Ki less than 1 nM (at pH 7.5, 0.50 M NaCl) while the Phe-Gly derivative is a much less potent competitive inhibitor with an apparent Ki = 0.20 microM under the same conditions and thus more suitable for use as an affinity ligand. Immobilization of these compounds via a 28-A spacer to agarose yields resins with binding capacities of greater than 7 mg of enzyme/mL of resin, while spacers of 22 A or less result in binding capacities at least 350 times smaller. Immobilized N-[1 (S)-carboxy-5-amino-pentyl]-L-Phe-Gly is superior to the Ala-Pro derivative because elution can be affected by raising the pH to 8.9 with 98% yields compared with only 20% from the latter. Thus, a three-step process involving detergent extraction, concentration by ammonium sulfate precipitation, and affinity chromatography on the resin-immobilized Phe-Gly derivative provides 30 mg of homogeneous ACE from 640 g of rabbit lung tissue. An ACE-like metalloprotease has also been isolated from testicular tissue by this same technique.

Treatment of prostatitis in the rat

A spontaneous, nonacute, age-dependent prostatitis was found in a high incidence in the lateral prostatic lobes of Lewis rats. Such rats were treated with methylprednisolone, indometacin , testosterone, hexyloxyphenylproprionate , polyestradiol phosphate, various antibiotics, or were caged together with female rats. The effect of the different treatment modalities was evaluated microscopically by blind observation of the degree of inflammatory reaction in the lateral prostate. Methylprednisolone and the testosterone ester caused a reduction of the inflammatory reactions and so did caging with female rats. The similarity of the rat prostatitis to the human condition may suggest the possibility of using corticosteroids or androgens for the treatment of patients with nonacute prostatitis.

Effects of continuous trichloroethylene inhalation on different strains of mice

Seven different strains of mice (wild, C57BL, DBA, B6CBA, A/sn, NZB and NMRI) were continuously exposed to 150 ppm trichloroethylene (TCE) during 30 days. After exposure all strains showed large increases in liver weight, while changes in kidney and spleen weights were small. Plasma butyrylcholinesterase (BuChE) activity increased in males of all strains and in females of strains A/sn and NZB. The increase in the females was less than that of the corresponding males. We concluded that there are moderate, but in some cases, significant differences in TCE sensitivity between different mouse strains. The differences observed between sexes emphasizes the importance of specifying sex as well as strain when reporting on toxic effects.

Trichloroethylene: further studies of the effects on body and organ weights and plasma butyrylcholinesterase activity in mice

The effects of continuous and intermittent inhalation of trichloroethylene (TCE) were studied in male and female mice. Plasma butyrylcholinesterase (BuChE) activity, body, liver, kidney and spleen weights were measured. The liver was studied histologically and motor activity measured with doppler radar. Continuous TCE-exposure (37-300 p.p.m.) increased plasma BuChE activity in the males in a time and concentration dependent manner. After 30 days at 37 p.p.m. the increase was about 25%. Exposure to 300 p.p.m. for 30 days increased the activity three times. BuChE activity in females was only slightly influenced even at 300 p.p.m. Liver weight was increased in a time and concentration dependent manner in both sexes. In animals continuously exposed for 30 days to 300 p.p.m., liver weight was roughly twice that of the air-exposed controls. Morphological changes were observed in the liver of TCE-exposed animals. Above 150 p.p.m. kidney weight in both sexes was significantly increased. This effect was more pronounced in the males than in the females. Spleen weight was not influenced by the exposure. Body weight increase was slightly lower in exposed animals. Plasma BuChE activity and liver weight returned to normal when exposure was terminated. Intermittent exposure to short pulses of high concentration of TCE had roughly the same effect on BuChE, body and organ weights as continuous exposure to the same time-weighted average. Motor activity was affected by the intermittent exposure schedules. At 900 p.p.m. decrease in activity was observed. At 3600 p.p.m. motor activity was considerably increased.

Circular dichroism and ordered structure of bisnucleoside oligophosphates and their Zn2+ and Mg2+ complexes

Circular dichroism, absorbance, hypochromicity, and the formation of Mg2+ and Zn2+ complexes have been measured for a series of bisnucleoside oligophosphates that contain adenosine, guanosine, and mixed guanosine/adenosine, guanosine/cytidine, and guanosine/uridine, as well as 7-methylguanosine and ribose-methylated purine nucleosides. All of the metal complex ions have stacking interactions at 2 degrees C, 10 mM tris(hydroxymethyl)aminomethane hydrochloride, pH 8.0. There is a measurable degree of base stacking for all unsubstituted purine nucleotides that differs, however, from that of bases in nucleic acids. The degree of base stacking varies with the length of oligophosphate chains and the state of methylation. The effect of 7-methylation of guanosine is interpreted as causing a switch of nucleic acid base stacking from an atypical to a typical mode, which could be important for cap function in mRNA. The Mg2+ and Zn2+ complexes give rise to characteristic circular dichroism. In all instances excepting 7-methylated bisguanosine oligophosphates, the active secondary structures are disrupted, and in this regard, Zn2+ is more effective than Mg2+. At least two sets of binding sites are involved. A single metal ion is bound tightly. Stability, in terms of equilibrium constants, increases by more than 1000-fold as a function of chain length varying from two to six phosphates. The consequences of methylation are only minor. Electrostatic attraction between metal ions and phosphates is the most likely mechanism of these phenomena as judged by the effect of high ionic strength.

Anion activation of angiotensin converting enzyme: dependence on nature of substrate

Anion activation of pulmonary angiotensin converting enzyme has been examined by using 23 furanacryloyl- and 3 benzoyl-tripeptides as substrates. Chloride stimulates hydrolysis of all substrates at least 24-fold. However, the kinetic mechanism, the amount of chloride required, and the effect of pH on activation, plus the relative activating potencies of various anions, are all strongly dependent on the substrate employed. Three substrate classes have been identified. Class I substrates appear to be hydrolyzed at pH 7.5 by an ordered bireactant mechanism in which anion must bind before substrate. The apparent activation constant (KA') for Cl- ranges from 75 to 150 mM at pH 7.5, doubles at pH 9.0, and decreases to about 3 mM at pH 6.0. Class II substrates, in contrast, are hydrolyzed by a nonessential activator mechanism. The kinetically determined KA' for Cl- at pH 7.5 ranges from 2.9 to 5.0 mM and changes only slightly with pH. Class III substrates are also hydrolyzed by a nonessential kinetic mechanism but one different from that followed by class II peptides. KA' values for Cl- at pH 7.5 measured with class III substrates are 18-30 mM. Class II substrates have Arg or Lys at the ultimate or penultimate position. The features distinguishing class I and III peptides are less clear, although all class III substrates identified have penultimate alanine residues. Possible explanations for this substrate dependence are offered.

One hundred fold increased activity of Aeromonas aminopeptidase by sequential substitutions with Ni(II) or Cu(II) followed by zinc

Full substitution of Cu(II) or Ni(II) for the two g-atom zinc in Aeromonas aminopeptidase hyperactivates the enzyme 6.5 and 25 fold respectively. Even greater enhancements of activity can be achieved with mixed metal substitutions. Thus, apoenzyme reactivated by first adding one g-atom zinc followed by one g-atom of either Cu(II) or Ni(II) is 15 and 22 times more active than the native enzyme. Reversing the order, i.e. by first adding either one g-atom Cu(II) or Ni(II) followed by one g-atom zinc, activates the enzyme nearly 100 fold. The order of metal addition is critical and suggests the existence of two non-identical metal sites, each with a different function.