Pulmonary angiotensin-converting enzyme antienzyme antibody

A method has been developed for quantitating anticatalytic activity in antibody preparations made in goats against pure solubilized angiotensin-converting enzyme from rabbit pulmonary membranes. Anticatalytic activity was purified about 90-fold from a single batch of serum by a procedure including diethylaminoethylcellulose chromatography and elution from Sepharose columns containing covalently bound pure enzyme. Antiholoenzyme antibody was fractionated with respect to charge and binding affinity; however, these different populations each inhibited enzymatic hydrolysis of hippurylhistidylleucine, angiotensin I, and bradykinin. The inhibition dose-response curves were similar for hydrolysis of hippurylhistidylleucine and angiotensin I despite the difference in molecular weight of these substrates. Evidence is presented suggesting that a single molecule of antibody can bind two molecules of enzyme and that at least 18% of the total antiholoenzyme antibody population is directed against determinants which influence catalytic activity. A competitive immunoassay was developed with radioiodinated pulmonary enzyme as displaceable antigen. The anticatalytic and radioimmune assays were used to examine immunological properties of converting enzymes in various rabbit organs and fluids. Kidney, brain, and serum were found to contain converting enzymes which were immunologically identified with that in rabbit lung. Converting enzyme in seminal plasma was similar to the lung enzyme in the anticatalytic assay, but showed lower immunoreactivity in the radioimmune assay.

Angiotensin-converting enzyme: vascular endothelial localization

Fluorescein-labeled antibody to rabbit pulmonary angiotensin-converting enzyme localized in the vascular endothelium of rabbit lung, liver, adrenal cortex, pancreas, kidney, and spleen. Epithelial cells of the renal proximal tubules were the only parenchymal cells among the organs studied that demonstrated immunoreactivity.

Morphological, histochemical, autoradiographic and topographical evidences of the origin of the Langerhans' cell from the melanocyte in the skin of the guinea pig

The microscopic anatomy of the nucleus, Golgi substance, mitochondria, etc. of type 1, 2, 3 and 4 albino melanocytes, type 01 and 011 albino intermediate cells of Billingham and Medawar and type I, II, III and IV albino Langerhans' cells of the albino guinea pig, is presented in detail. The study has demonstrated that the albino melanocytes degenerate through sequential stages of intermediate cells of Billingham and Medawar, type I, II and III Langerhans' cells to ultimately from type IV Langerhans' cells. It has been shown that all the dendritic cells of the epidermis belonged to one class of cells. Autoradiographic techniques have shown that type 3 and type 4 melanocytes, respectively, bearing 6 and 5 round-tipped dendritic processes, divide by mitosis to form two daughter cells. One of these two daughter forms the intermediate cell of Billingham and Medawar. This cell, while transforming sequentially into type I, II, III and IV Langerhans' cells, moves up through the Malpighian and granular layers of cells, to the stratum corneum. This type IV Langerhans' cell is ultimately extruded out of the stratum corneum by exfoliation. The other daughter melanocyte remains at its place in the sub-basal zone to function as a mature melanocyte. The time for the passage of the daughter melanocyte to travel from the sub-basal zone to the stratum corneum layer was found to be 15 days.

Thio derivatives of b-diketones and their metal chelates. XXII. Dipole moments of some bivalent and trivalent metal complexes of fluorinated monothio-b-diketones

Dipole moments have been determined by static polarization measurements for some iron(111), ruthenium(111), rhodium(111), nickel(11), palladium(11), platinum(11), copper(11) and zinc(11) complexes of fluorinated monothio-β-diketones RC(SH)=CHCOCF3. The moments indicate a facial-octahedral configuration for the iron, ruthenium and rhodium complexes, a cis-square-planar configuration for the nickel, palladium and platinum complexes, and a tetrahedral configuration for the zinc complexes. The copper complexes have moments 0.5-1.0 D lower than the mean value for the corresponding nickel, palladium and platinum complexes; this lowering of the moment is attributed to significant distortion from the square-planar towards the tetrahedral configuration. The dipole moments of the square-planar and octahedral complexes decrease if the R groups are arranged in the order: p-MeC6H4 ≥ 2-thienyl > β-naphthyl > m-MeC6H4 > Ph > Pr? > Bui > Me > m-ClC6H4 > m-BrC6H4 > p-FC6H4 > p-ClC6H4 > p-BrC6H4 > m,p-Cl2C6H3.

Pulmonary angiotensin-converting enzyme. Structural and catalytic properties

Angiotensin-converting enzyme has been solubilized from a particulate fraction of rabbit lung and purified to apparent homogeneity in 11% yield by a procedure including fractionation with DEAE-cellulose and calcium phosphate gel, elution from Sephadex G-200, and lectin affinity chromatography. The molecular weight estimated by equilibrium sedimentation was approximately 129,000, either in the absence or presence of 6 M guanidine hydrochloride. A slightly higher value of 140,000 determined for the reduced, denatured protein by gel electrophoresis in the presence of sodium dodecyl sulfate and a much higher figure derived from gel filtration are probably due to the glycoprotein nature of the enzyme. Its oligosaccharide content accounted for 26% of the weight calculated from its amino acid and carbohydrate composition. The estimated content of sugar residues per mole was: galactose, 57; N-acetylglucosamine, 53; mannose, 43; N-acetylneuraminic acid, 19; and fucose, 4. Threonine and alanine were identified, respectively, as NH2-terminal and COOH-terminal residues by the dansylation procedure and by digestion with carboxypeptidase A. The enzyme was found to contain approximately 1 g atom of zinc per mol. Km values for hydrolysis of hippurylhistidylleucine and angiotensin I were 2.3 and 0.07 mM, and the corresponding turnover numbers were 15,430 and 792 mol/min/mol at 37 degrees. Bradykinin was also a substrate, and release of its COOH-terminal dipeptide, Phe-Arg, was catalyzed at a comparable rate to that of His-Leu from the COOH terminus of angiotensin I. Enzyme activity required the presence of chloride ions and was inhibited by EDTA and by low concentrations of Bothrops bradykinin-potentiating peptides. In addition, hydrolysis of hippurylhistidylleucine was inhibited competitively by other defined peptides, including di- and tripeptides, which were not substrates.

Studies on a wide-spectrum intestinal dipeptide uptake system in the monkey and in the human

1. The intestinal transport of glycine and leucine residues of glycyl-L-leucine was studied in the monkey and in the human in vitro. Uptake of both [14C]glycyl-L-leuine and glycyl-L-[14C]leucine show similar Kt values, but there is a marked difference in the Vmax. values. Preliminary studies suggest that this anomalous difference in the Vmax. values may be due to the greater efflux rate of glycine from the tissue. 2. Arrhenius plots of both [14C]glycyl-L-leucine uptake and glycyl-L-[14C]leucine uptake in the monkey intestine show a discontinuity at about 20 degrees C. The activation energies above and below the discontinuity are similar for both [14C]glycyl-L-leucine uptake and glycyl-L-[14C]leucine uptake. These similarities in uptake characteristics suggest that the dipeptide glycyl-L-leucine is transported as one unit. 3. In the monkey intestine, glycyl-L-leucine uptake is inhibited by a wide variety of dipeptides, including those containing acidic and basic amino acids. The inhibition was shown to be competitive by using four representative dipeptides namely: L-alanyl-L-alanine, L-alanyl-L-leucine, L-glutamyl-L-glutamic acid and L-lysyl-L-lysine. The results strongly suggest that in the monkey intestine there may be a dipeptide-uptake system with an extremely broad specificity. These results were also confirmed in the human in a limited way.

Thio derivatives of β-diketones and their metal chelates. XVIII. Mass spectra of some metal chelates of the monothio derivatives of benzoylacetone anddibenzoylmethane

The mass spectra of the iron(III), cobalt(III), nickel(II) and zinc(II) complexes of the monothio-β-diketones RC(SH)=CHCOPh (R = Me, Ph) have been obtained. The iron and cobalt complexes of 3-mercapto-1-phenylbut- 2-en-1-one (R = Me) do not give a peak for the molecular ion due to thermal degradation to the bivalent metal complex Met(MeCS=CHCOPh)2 (Met = Fe, Co), which then undergoes reactions similar to those undergone by the nickel and zinc complexes. The most interesting feature of the spectra is the loss of hydrogen sulphide which does not occur with the free ligand or with metal complexes of fluorinated monothio-8-diketones RC(SH)=CHCOCF3. ��� The zinc complex of 3-mercapto-1,3-diphenylprop-2-en-1-one (R = Ph) undergoes fragmentation in the mass spectrometer to produce inter alia [ZnC6H5]+. However, the iron(III), cobalt(III), nickel(II) and palladium(II) complexes undergo thermal degradation in the mass spectrometer but the mass spectra of these four complexes give metal-free ions with m/e greater than m/e for L, due to fragmentation of the ion 2L.

Mass spectral studies of lanthanide chelates. I. Samarium, europium, gadolinium and terbium chelates of thenoyltrifluoroacetone

The mass spectra of the lanthanide chelates of thenoyltrifluoroacetone, viz. Met{CF3COCH=C(O-)-C4H3S}3 (Met = Sm, Eu, Gd, Tb), have been obtained. All four spectra display similar fragmentation patterns. Fluorine migration to the metal with the concomitant loss of :CF2 occurs with all four lanthanide chelates. Peaks were observed for the ions [MetF2]+ (Met = Sm, Gd, Tb) and [MetF]+ (Met = Sm, Eu). The occurrence of [MetF]+ in the spectra of the samarium and europium chelates is in keeping with the tendency of these two lanthanides to be reduced to the bivalent state. On the other hand, oxidation of terbium(III) to terbium(IV) was not observed in the mass spectra.

A comparative study of the distribution of soluble and particulate glycyl-L-leucine hydrolase in the small intestine

1. A comparative study has been made of glycyl-l-leucine hydrolase activity in the soluble and particulate fractions of intestinal mucosa from monkey, guinea-pig, rabbit and rat. The specific activity of the soluble enzyme is very high in monkey and guinea-pig, and lower in rabbit and rat. The particulate enzymes from all the four species show low specific activities and form 1–10% of the total activity.

2. The pH optima in all cases lie in the range 7·6–7·8. The Km values of the substrate were similar for both soluble and particulate enzyme from monkey and guinea-pig, but in the rabbit and rat the Km value with the particulate enzyme was higher than with the soluble enzyme.

3. The particulate enzyme activity in all cases was the highest in the distal regions of the intestine, whereas the soluble enzyme showed maximal activity in the proximal and middle regions.

Thio derivatives of β-Diketones and their metal chelates. XV. Mass spectra of cobalt(III) and rhodium(III) chelates of some fluorinated Monothio-β-diketones

The mass spectra of the cobalt(111) and rhodium(111) chelates of the fluorinated monothio-β-diketones RC(SH)=CHCOCF3 (R = Ph, p-MeC6H4, p-BrC6H4, p-FC6H4, and 2-thienyl) and of the cobalt(111) chelate of CH3C(SH)=CHCOCF3 have been obtained. The cobalt chelates do not give a peak for the molecular ion because of thermal degradation to the cobalt(11) complex CO(RCS=CHCOCF3)2, which then undergoes reactions in the mass spectrometer. Fluorine migration occurs with cobalt but not with rhodium. The cobalt complexes give rise to more metal-containing fragments than their rhodium analogues. Mechanisms are proposed for the reactions involving the metal-containing fragments. Cobalt undergoes valency changes to give cobalt(11) and cobalt(1) complex ions, whereas rhodium undergoes a valency change to the bivalent state only.

Thio derivatives of β-diketones and their metal chelates. XIV. Mass spectra of palladium and platinum chelates of some fluorinated Monothio-β-diketones

The mass spectra of the palladium(11) and platinum(11) chelates of the fluorinated monothio-β- diketones, RC(SH)=CHCOCF3 (R = Ph, p-MeC6H4, p-BrC6H4, p-NO2C6H4, 2-thienyl), and of the palladium chelate of CH3C(SH)=CHCOCF3 have been obtained. The platinum chelates give rise to more metal-containing peaks than the palladium chelates. Mechanisms are proposed for the reactions involving the metal-containing fragments. A comparison of the mass spectra of the zinc, nickel, palladium and platinum chelates of these fluorinated monothio-β-diketones reveals that the fragmentation pattern is determined by the metal.

Hydrolysis of Monothio-β-diketones. II. Hydrolysis of three fluorinated Monothio-β-diketones

The rapid decomposition of the fluorinated monothio-β-diketones RC(SH)=CHCOCF3, 4-(3?-bromophenyl)-1,1,1-trifluoro-4-mercaptobut-3-en-2- one (R = m-BrC6H4), 4-(4?-bromophenyl)-1,1,1-trifluoro-4-mercaptobut-3- en-2-one (R = p-BrC6H4) and 1,1,1-trifluoro-4-mercaptopent-3-en-2-one(R = Me), in acid solution has been shown to occur by hydrolytic cleavage to yield the ketone RCOCH3, hydrogen sulphide and probably trifluoroacetic acid. The pseudo first-order rate constants for these compounds are (8.0�0.3)x 10-3, min-1, (6.0 � 0.6) x 10-3 min-1 and 0.12�0.01 min-1, respectively. The greater vulnerability of 1,1,1- trifluoro-4-mercaptopent-3-en-2-one, compared to the other two monothio-β-diketones, towards hydrolytic cleavage is related to the nature of the R substituent in that conjugation involving the terminal aromatic ring stabilizes the monothio-β-diketone.

Thio derivatives of β-Diketones and their metal chelates. XVII. Mass spectra of iron(III) and ruthenium(III) chelates of some fluorinated Monothio-β-diketones

The mass spectra of the iron(111) and rhodium(111) chelates of the fluorinated monothio-β-diketones RC(SH)=CHCOCF3 (R = Ph,p-MeC6H4, 2-thienyl) have been obtained. Whereas the ruthenium(111) chelates give a peak for the molecular ion, the iron(111) chelates do not, due to thermal degradation to the iron(11) complex Fe(RCS=CHCOCF3)2 which then undergoes reactions in the mass spectrometer. Fluorine migration occurs with two of the iron chelates but not with the ruthenium chelates. Mechanisms are proposed for the reactions of the ruthenium chelates.

Thio derivatives of b-diketones and their metal chelates. XIII. Mass spectra of zinc and nickel chelates of some fluorinated monothio-b-diketones

The mass spectra of the zinc(11) and nickel(11) chelates of four fluorinated monothio-β-diketones, RC(SH)=CHCOCF3 (R = Ph, p-MeC6H4, 2-thienyl, Me), have been obtained. The mass spectra of the nickel chelates have considerably more peaks due to metal-containing species than the spectra of the zinc chelates, while the reverse is true for the metal-free fragments. All the zinc chelates give peaks for M (molecular ion), M ? CF3, M - L (LH = monothio-β-diketone), M - L ? CF2, LH, L, L - F, RCSCH and RCS. All the nickel chelates give peaks for M, M - F, M ? CF3, M - COCF3, M - L, M- 2L and L. In addition, some of the metal chelates give other peaks. Mechanisms are proposed for the reactions giving rise to some of these species. All the zinc and nickel chelates give a strong peak due to L+ arising from a valence change of the metal ion from the bivalent to the univalent state as follows: [Me11L2]+ → L+ + Me1L (Me = Zn, Ni). It is suggested that the ion L+ has a resonance-stabilized cyclic structure.

Thio derivatives of β-diketones and their metal chelates. XVI. Nickel(II), palladium(II), platinum(II), zinc(II) and cobalt(III) chelates of some new fluorinated Monothio-β-diketones

The new fluorinated β-diketones RCOCH2COCF3 (R = p-ClC6H4, m-ClC6H4, m-BrC6H4, m-MeC6H4 and m,p-C1,C6H3) have been prepared. The monothio-β-diketones RC(SH)=CHCOCF3 derived from these β-diketones were also prepared. Complexes of these monothio-β-diketones and of p-FC6H4C(SH)=CHCOCF3 with nickel(11), palladium(11), platinum(11), zinc(11) and coba1t(111) have been prepared and characterized. All the complexes are stable and display sharp melting points.

Glycyl-L-leucine hydrolase, a versatile 'master' dipeptidase from monkey small intestine

1. A highly active and electrophoretically homogeneous dipeptidase was purified from the soluble extracts of monkey small-intestinal mucosa. 2. By gel-filtration studies the molecular weight of the enzyme was found to be 107000. It is composed of two identical, subunits of molecular weight 54000. 3. A paper-chromatographic method of dipeptidase assay was developed to overcome some of the difficulties encountered in the generally used spectrophotometric procedure. By using this method, the K(m) and k(0) values of a few substrates were determined. 4. The substrate specificity of the enzyme was investigated in great detail with substrates of a wide range of possible structural types. The enzyme hydrolyses a very large proportion of the range of dipeptides tested. This enzyme, which exhibits such a wide range of action, has been termed the ;master' dipeptidase of the intestine. Glycylglycine, glycyl-l-proline, glycyl-l-histidine, l-prolylglycine and some of the arginine- and aspartic acid-containing dipeptides were not substrates and are possibly hydrolysed by other peptidases. These results therefore suggest that in the intestine the number of dipeptidases is rather limited. 5. In the light of these findings, the implications on the role of dipeptidases in intestinal peptide transport are discussed.