Dihydrofluorouracil, a fluorouracil catabolite with antitumor activity in murine and human cells

Dihydrofluorouracil (FUH2), the initial catabolite of 5-fluorouracil (FUra), was examined to determine whether this derivative had antitumor activity or host cell (bone marrow) toxicity. Studies were undertaken with Ehrlich ascites tumor and bone marrow cells isolated from CF-1 mice. Cells were exposed for 1 h either to no drug (control) or to varying concentrations, ranging from 1 to 250 microM, of either FUra, FUH2, or alpha-fluoro-beta-alanine. Cells were then cultured and colony formation was assessed after 10 to 14 days. Ehrlich ascites tumor cells were more sensitive to FUra [50% lethal dose (LD50) = 18 microM] than to FUH2 [LD50 = 50 microM], with no sensitivity to alpha-fluoro-beta-alanine even at 250 microM. Bone marrow cells had a toxicity profile similar to that of FUra (LD50 = 10 microM) but were relatively insensitive to FUH2 (LD50 greater than 250 microM), with no sensitivity to alpha-fluoro-beta-alanine. Subsequent studies examined colony formation of the human breast carcinoma cell line MCF-7 following 1 h exposure to varying concentrations of FUra and FUH2. These cells were less sensitive to both FUra (LD50 approximately 80 microM) and FUH2 (LD50 approximately 350 microM). Initial studies on the mechanism of toxicity of FUH2 demonstrated that this FUra catabolite could produce inhibition of thymidylate synthase activity in Ehrlich ascites tumor cells with a pattern similar to that resulting from exposure to FUra. This is the first study to demonstrate that FUH2 (a quantitatively important catabolite of FUra) is cytotoxic, and it suggests that FUH2 may contribute to the toxicity of FUra in vivo, possibly by being anabolized to FUra.

Effect of hydration and dehydration on technetium-99m CO2 DADS renal studies in normal volunteers

Ten normal volunteers were studied in the hydrated and dehydrated states with the new renal radiopharmaceutical technetium-99m N,N'-bis(mercapto acetyl)-2, 3-diaminopropanoate [( 99mTc]CO2 DADS). The data were used to determine the effect of hydration and dehydration and to determine the normal range in each state. Visual evaluation of the images indicated that the first appearance of tracer in the collecting system was approximately the same in either state, that the concentration of tracer in the collecting system was always higher in the dehydrated state (p less than 0.01), and that the ureters always appeared more segmented in the dehydrated state (p less than 0.01). Quantitative analysis of the images indicated that the kidney to background ratio 1-2 min after injection was somewhat greater in the dehydrated state (13.5 +/- 4.0) than in the hydrated state (9.8 +/- 2.2) (p less than 0.05), that the size of the bladder was always greater in the hydrated state (p less than 0.05), and there was no difference in the amount of tracer in the bladder at 30 min after injection. The results define the normal hydrated and dehydrated [99mTc]CO2 DADS renal study and identify several differences between the two states which can be explained primarily by differences in urine flow rates.

Complete urinary excretion profile of 5-fluorouracil during a six-day chemotherapeutic schedule, as resolved by 19F nuclear magnetic resonance

We determined the urinary excretion of 5-fluorouracil (5FU) and its metabolites during six days of chemotherapy, using the non-invasive approach of 19F nuclear magnetic resonance. With this method, which requires no labeled drug, one can study the biological sample directly and simultaneously identify and quantify all the fluorinated metabolites. The daily urinary excretion of 5FU and its metabolites was high (94.8% of 5FU administered) and nearly constant all during the treatment. By far the major excreted catabolite was alpha-fluoro-beta-alanine, which made up 78.9% of the total. Unchanged 5FU (10.8% of dose injected) was found only during the first 2 h after injection. We observed neither accumulation of 5FU nor modifications in its metabolism during the treatment.

Synthetic derivatives of N3-fumaroyl-L-2,3-diaminopropanoic acid inactivate glucosamine synthetase from Candida albicans

Synthetic derivatives of N3-fumaroyl-L-2,3-diaminopropanoic acid constitute the novel group of glutamine analogs. They are powerful, competitive inhibitors of the glucosamine synthetase (2-amino-2-deoxy-D-glucose-6-phosphate ketol-isomerase (amino-transferring), EC 5.3.1.19) from Candida albicans with respect to glutamine and uncompetitive with respect to D-fructose 6-phosphate. Some of the compounds tested irreversibly inactivate glucosamine synthetase with Kinact values of 10(-4) to 10(-6) M. The addition of glutamine protects enzyme from the inactivation, while the absence of D-fructose 6-phosphate lowers the rate of inactivation. An ordered, sequential mechanism is suggested for binding of the inhibitors to the glutamine-binding site. A number of tested compounds act as active-site-directed, irreversible inhibitors. It is suggested that derivatives of N3-fumaroyl-L-2,3-diaminopropanoic acid should be classified as mechanism-based enzyme inactivators. Structural requirements for an effective inactivator containing N3-fumaroyl-L-2,3-diaminopropanoic acid moiety are discussed.

beta-N-Oxalylamino-L-alanine: action on high-affinity transport of neurotransmitters in rat brain and spinal cord synaptosomes

beta-N-Oxalylamino-L-alanine (BOAA) is a dicarboxylic diamino acid present in Lathyrus sativus (chickling pea). Excessive oral intake of this legume in remote areas of the world causes humans and animals to develop a type of spastic paraparesis known as lathyrism. BOAA is one of several neuroactive glutamate analogs reported to stimulate excitatory receptors and, in high concentrations, cause neuronal vacuolation and necrosis. The present study investigates the action of BOAA in vitro on CNS high-affinity transport systems for glutamate, gamma-aminobutyric acid (GABA), aspartate, glycine, and choline and in the activity of glutamate decarboxylase (GAD), the rate-limiting enzyme in the decarboxylation of glutamate to GABA. Crude synaptosomal fractions (P2) from rat brain and spinal cord were used for all studies. [3H]Aspartate transport in brain and spinal cord synaptosomes was reduced as a function of BOAA concentration, with reductions to 40 and 30% of control values, respectively, after 15-min preincubation with 1 mM BOAA. Under similar conditions, transport of [3H]glutamate was reduced to 74% (brain) and 60% (spinal cord) of control values. High-affinity transport of [3H]GABA, [3H]glycine, and [3H]choline, and the enzyme activity of GAD, were unaffected by 1 mM BOAA. While these data are consistent with the excitotoxic (convulsant) activity of BOAA, their relationship to the pathogenesis of lathyrism is unknown.

Studies of peptide antibiotics. XLVI. Syntheses of gramicidin S analogs containing D-alpha,beta-diaminopropionic acid or alpha,beta-dehydroalanine

A gramicidin S (GS) analog ([D-Dpr4,4'] GS) containing D-alpha,beta-diaminopropionic acid (D-Dpr) in place of D-Phe at 4,4' positions was derived from [L-Orn(delta-formyl)2,2', D-Dpr(beta-Z)4,4']GS, which was synthesized by conventional method in solution. An analog [delta Ala4,4']GS was synthesized from [L-Orn(delta-Boc)2,2', D-Dpr4,4']GS through Hofmann degradation of the D-Dpr residues. Antimicrobial activities of these analogs were tested; [D-Dpr(beta-Z)4,4']GS and [delta Ala4,4']GS showed high antimicrobial activities against Gram-positive bacteria. [D-Dpr4,4']-GS showed an appreciable activity against Gram-negative bacteria such as Escherichia coli. Four semigramicidin S (semiGS) analogs such as [delta Ala4]semiGS were synthesized; these had no antimicrobial activity. Analogs containing delta Ala residues were hydrogenated, and the formation of L-Ala or D-Ala residues was determined. The delta Ala residues in [delta Ala4,4'] GS were reduced to DL-Ala, and delta Ala in [delta Ala4]semiGS mostly to L-Ala. The relationships of the antimicrobial activity, CD curves and asymmetric hydrogenation to the structure were discussed.

Metabolism of uridine and determination of liver ribonucleic acid synthesis in developing and adult mice

The metabolism of [5-3H]uridine and the incorporation of the precursor into liver RNA was studied in developing (13-day-old) and adult (45-day-old) mice. Different time-courses of labelling and increased amounts of labelled catabolic products of uridine were found in liver and blood of developing mice compared with adult animals. This is suggested to be a consequence of enlarged metabolite pools resulting from a lower total amount of uracil-degrading enzymes in the developing mice. The labelling of the uracil nucleotides was decreased in the developing liver. However, in spite of a lower specific radioactivity of UTP, the RNA-specific radioactivity of developing liver was increased compared with adult liver. Also the labelling of liver RNA with [6-14C]orotic acid was found to be increased in developing mice, thus indicating a higher rate of RNA synthesis in these animals. A more pronounced difference in liver RNA labelling between the developing and the adult mice obtained with the use of [14C]orotic acid than with [3H]uridine may suggest that the de novo pathway, relative to the salvage pathways, is more important in developing than in adult liver.

Inactivation of the dadB Salmonella typhimurium alanine racemase by D and L isomers of beta-substituted alanines: kinetics, stoichiometry, active site peptide sequencing, and reaction mechanism

The pyridoxal phosphate dependent Salmonella typhimurium dadB alanine racemase was inactivated with D- and L-beta-fluoroalanine, D- and L-beta-chloroalanine, and O-acetyl-D-serine. Enzyme inactivation with each isomer of beta-chloro[14C]alanine followed by NaBH4 reduction and trypsin digestion afforded a single radiolabeled peptide. In the same manner, NaB3H4-reduced native enzyme gave a single labeled peptide after trypsin digestion. Purification and sequencing of these three radioactive peptides revealed them to be a common, unique hexadecapeptide which contained labeled lysine at position 6 in each case. Enzyme which had been inactivated, but not reductively stabilized with NaBH4, released a labile pyridoxal phosphate-inactivator adduct on denaturation. The structure of this adduct suggests that the enzyme was inactivated by trapping the coenzyme in a ternary adduct with inactivator and the active site lysine. Under denaturing conditions, facile alpha,beta-elimination occurred, releasing the aldol adduct of pyruvate and pyridoxal phosphate. Reduction of the ternary enzyme adduct blocked this elimination pathway. The overall mechanism of racemase inactivation is discussed in light of these results.

Inactivation of the Pseudomonas striata broad specificity amino acid racemase by D and L isomers of beta-substituted alanines: kinetics, stoichiometry, active site peptide, and mechanistic studies

Mechanism-based inactivators were used to probe the active site of the broad specificity amino acid racemase from Pseudomonas striata. Kinetic parameters for the inactivation of the racemase with both stereoisomers of beta-fluoroalanine, beta-chloroalanine, and O-acetylserine were determined. By use of 14C-labeled O-acetylserines, the stoichiometry of inactivator binding was found to be one inactivator bound per enzyme subunit. The PLP-dependent enzyme contains one coenzyme per subunit, and after NaB3H4 reduction of the PLP-imine bond, followed by trypsin digestion of the protein, the amino acid sequence of the PLP-binding peptide was determined. Trypsin digestion of the enzyme labeled with either L or D isomer of O-acetylserine and sequencing of the labeled peptide revealed that the inactivators bind to the same lysine residue which binds PLP in native enzyme. The characterization of a PLP adduct released from inactivated enzyme under some conditions is also described. Implications of the formation of this compound with respect to the overall reaction mechanism of inactivation are discussed.

A method for the synthesis of [14C]-kynurenine

A new method is described for the synthesis of [14C]-labelled L-kynurenine from [14C]-L-tryptophan, using extracts of tryptophan-adapted cells of Pseudomonas marginalis. It is based on the selective, rapid inactivation of kynureninase by a newly discovered inhibitor of this enzyme, 3-chloro-L-alanine. The yield of [14C]-kynurenine produced in this manner is 76% theoretical.

Mechanism-based inactivation of bacterial kynureninase by beta-substituted amino acids

Kynureninase from Pseudomonas marginalis has been shown to catalyze the elimination of beta-functionalities of beta-substituted amino acids such as beta-chloro-L-alanine, resulting in the formation of aminoacrylate-pyridoxal phosphate-enzyme complex. This intermediate can be processed further to produce either pyruvate, ammonia, and active enzyme or an inactive enzyme complex. Approximately 1 in 500 turnovers leads to inactivation of the enzyme. The mechanism of inactivation appears to involve nucleophilic addition of a carboxylate group at the active site to the beta-carbon of the aminoacrylate complex. Both subunits of kynureninase have been shown to be catalytically competent although the native enzyme contains only one pyridoxal phosphate per dimer. Since both aspartate beta-decarboxylase and kynureninase catalyze mechanistically similar reactions, these results further support the notion that the two active sites may have several common features.

A mathematical model of the kinetics of 5-fluorouracil and its catabolites in freshly isolated rat hepatocytes

A mathematical model for the kinetics of 5-fluorouracil (FUra) catabolism in liver cells is proposed. It is based on published data for the metabolism of FUra by isolated rat hepatocytes. The model relies on biochemical knowledge of the catabolic pathway. The key-steps are: the cellular uptake and the conversion of the unchanged drug to dihydrofluorouracil (FUH2) and subsequently to alpha-fluoro-beta-alanine (FBAL); the cellular fluxes of the 2 catabolites, FUH2 and FBAL. Water is partitioned between the extracellular and intracellular spaces. The first step is described by Michaelis-Menten kinetics and the other processes by first-order kinetics. Satisfactory fitting of the model validates these simplifications and provides values for the parameters describing the process. The model indicates that the kinetics of FUra disappearance are non linear, the Vmax of the first step being between 3.1 and 5.0 microM/min and the Km between 12 and 37 microM; the rate limiting step is the degradation of FUH2 (the major intracellular catabolite) with a rate constant of 0.1 to 0.02 min-1; the FUH2 transmembrane exchange is active; the exchange of the final catabolite FBAL is by diffusion.

Inactivation of glucosamine-6-phosphate synthetase from Salmonella typhimurium LT 2 SL 1027 by N beta-fumarylcarboxyamido-L-2,3-diamino-propionic acid

N beta- fumarylcarboxyamido -L-2,3-diaminopropionic acid ( FCDP ), a novel glutamine analog, inhibits the reaction of glucosamine-6-phosphate synthetase (EC 5.3.1.19) from Salmonella typhimurium LT 2 by irreversible inactivation of the enzyme. The kinetic data on enzyme inhibition and inactivation are presented. It is suggested that the enzyme inactivation occurs according to a sequential mechanism.

Isolation and analysis of two Escherichia coli K-12 ilv attenuator deletion mutants with high-level constitutive expression of an ilv-lac fusion operon

A lysogenizing lambda phage, lambda dilv-lac11, was constructed to carry an ilvD-lac operon fusion. Expression from the phage of the ilvE and lacZ genes is controlled by an intact ilv control region also carried by this phage. Two spontaneous mutants of lambda dilv-lac11 that have high-level constitutive expression of the ilv-lac fusion operon were isolated by growth on a beta-chloroalanine selective medium. The mutants were shown by nucleotide sequence determination to contain large deletions (delta 2216, approximately 1.6 kilobases; delta 2219, approximately 1.9 kilobases), which in both cases remove the proposed ilv attenuator terminator. The rest of the ilv leader and promoter region DNA remains intact in these mutants. Deletion 2216 also removed part of the downstream ilvG gene, whereas delta 2219 extended through the entire ilvG gene into the ilvGE intercistronic region. A possible mechanism of deletion formation is discussed.

Effect of coadministration of uracil on the toxicity of tegafur

The cardiotoxic and neurotoxic effects of tegafur, an anticancer agent, were compared with those of uracil plus tegafur (4:1 mol/mol) in mice, rats, rabbits, cats and dogs. Uracil plus tegafur was shown to be less toxic than the drug alone in all the species, and uracil was found to decrease the toxicity of tegafur. alpha-Fluoro-beta-alanine, a catabolic metabolite of the drug, had toxic effects similar to tegafur. The results suggest that administration of uracil with tegafur prevents the side effects of the drug on the heart and CNS by inhibiting the degradation of 5-fluorouracil.

N,N'-bis(S-benzoylmercaptoacetamido) ethylenediamine and propylenediamine ligands as renal function imaging agents. I. Alternate synthetic methods

A new method was developed to synthesize tetradentate ligands containing the N,N'-bis(S- benzoylmercaptoacetyl ) ethylenediamine and propylenediamine moieties (DADS compounds). Methods are also represented with which to synthesize some of the positional isomers of the above compounds. These isomers represent a new class of compounds. A total of 21 different compounds were prepared. These will be used in an effort to establish a relationship between structure and renal imaging properties.

Iron-bleomycin-deoxyribonucleic acid system. Evidence of deoxyribonucleic acid interaction with the alpha-amino group of the beta-aminoalanine moiety

The Fe(III) complex of bleomycin (BLM) is, at pH 4, in the high-spin form. At pH 7, the coordination of the alpha-amino group of the beta-aminoalanine moiety of BLM converts it to a low-spin species: BLM X Fe(III) X alpha NH2. The conversion of the high-spin species to the low-spin one can also take place at pH 4 (i) by addition of ligands L such as N3-, S2O3(2-), and SCN- or (ii) through interaction with DNA. Moreover, the addition, at pH 7, of DNA to BLM X Fe(III) that has been previously complexed with one of these ligands L displaces this latter from its position. These results suggest that (i) the ligand L occupies the same site of coordination as the alpha-amino group and (ii) an interaction occurs between the beta-aminoalanine moiety of BLM and DNA that lowers the pKd of the alpha-amino group, promoting its coordination to iron.

Clinical evaluation of Tc-99m N,N'-bis(mercaptoacetyl)-2,3-diaminopropanoate as a replacement for I-131 hippurate: concise communication

A clinical comparison of Tc-99m N,N'-bis( mercaptoacetyl )-2,3- diaminopropanoate (Component A) (Tc-99m CO2-DADS-A) and I-131 hippurate was conducted in a series of five normal volunteers and 18 patients. Each subject was studied in one session with Tc-99m CO2-DADS-A and I-131-hippurate; digital and analog images were recorded for 30 min and after voiding. In the normal volunteers, digital images with Tc-99m CO2-DADS-A gave a kidney-to-background ratio at 3 min that was greater relative to I-131 hippurate, a leading-edge parenchymal transit time that was similar to I-131 hippurate, and a percent injected dose in the urine at 30 min that was slightly less than I-131 hippurate (p less than 0.05). In patients (serum creatinine 1.0 to 14.3 mg/dl), decreasing renal function impaired excretion of Tc-99m CO2-DADS-A more than that of I-131 hippurate (p less than 0.01). In analog images, Tc-99m CO2-DADS-A always gave superior spatial resolution. No evidence of hepatobiliary excretion was detected with either radiopharmaceutical. We conclude that Tc-99m CO2-DADS-A and similar compounds should be pursued as possible replacements for I-131 hippurate.

Lathyrus excitotoxin: mechanism of neuronal excitation by L-2-oxalylamino-3-amino- and L-3-oxalylamino-2-amino-propionic acid

Intracellular recordings were made in cultured neurones from foetal mouse spinal cord. The effects of applications of the neurotoxin, L-3-oxalylamino-2-amino-propionic acid (a constituent of the chickling pea, Lathyrus sativus) and its 2-oxalylamino isomer on membrane potential and conductance were examined in the presence of TTX and TEA and compared to those of other excitatory amino acids. Although both compounds produced membrane depolarization and an increase in input conductance, the 3-oxalylamino isomer (beta-ODAP) was approximately equal to 10 times more potent than the 2-oxalylamino isomer (alpha-ODAP). beta-ODAP caused a voltage-independent change in conductance, as compared to an apparent voltage-dependent decrease produced in the same neurons by L-aspartic acid (L-ASP). Although reversal potentials determined for beta-ODAP resembled those for alpha-ODAP and kainic acid, they were consistently and significantly lower than the reversal level for L-ASP. Although the receptor antagonist 2-amino-5-phosphonovaleric acid (APV) and the divalent cation Cd2+ did not alter the conductance increase evoked by beta-ODAP, they markedly depressed responses to L-ASP. Such differences suggest a mechanism of excitatory action for the neurotoxin, beta-ODAP, which does not involve a Ca2+-dependent mechanism and is quite different from that for L-ASP and N-methyl-D-aspartic acid, but similar to that of kainic and quisqualic acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloralanyl and propargylglycyl dipeptides. Suicide substrate containing antibacterials

A set of dipeptides containing the amino acid residues beta-chloroalanine and propargylglycine, which are mechanism-based inactivators of purified microbial enzymes (alanine racemase and cystathionine gamma-synthase, respectively), have been synthesized, and their antibacterial properties in vitro have been evaluated. Dipeptides containing a single beta-chloro-L-alanyl residue (e.g., 3, 5, 9, and 10) or a single L-propargylglycyl residue (e.g., 12 and 15) are potent antibacterials. The in vitro antibiotic activity of beta-chloro-L-alanine and of L-propargylglycine is increased as much as 4000-fold by incorporation of these residues into a dipeptide. Compounds that contain only a single enzyme-inactivating amino acid together with a second L-alanyl residue (3, 5, 12, and 15) have a restricted range of activity: of the species tested, only Streptococcus agalactiae, Staphylococcus aureus, and Staphylococcus epidermidis are sensitive. However, peptides that contain two suicide-substrate residues [e.g., beta-Cl-LAla-beta-Cl-LAla (8) or LppGly-LppGly (18)] are broad-spectrum antibacterials; as many as 12 different species of the 16 surveyed are sensitive. Dipeptides that contain an amino-terminal L-methionyl (9) or an L-norvalyl (10) residue and a carboxy-terminal beta-chloro-L-alanyl unit are also effective against a large number of organisms; the spectra of activity are like those seen for 8 and 18. A "mixed" dipeptide [beta-Cl-LAla-LppGly, (21)] gives apparent synergism of antibiotic action of beta-chloro-L-alanine and of L-propargylglycine when these two residues are incorporated into a single structure. Peptides of the D,D configuration (4, 6, 13, 16, and 20) and ones of L,D stereochemistry (e.g., 7) are not antibacterials. Peptides containing one (11 and 14) and two (17) D,L-propargylglycyl residues are unresolved sets of diastereomers; the mixtures of compounds are between two- and fourfold less active than the correspondingly resolved L,L dipeptides (12, 15, and 18). These findings are consistent with a mechanism of action for these antibiotics involving stereoselective processing of the peptidyl unit in vivo.

Lathyrism: a neurotoxic disease

Lathyrism, one of the oldest neurotoxic diseases known to Man, results from excessive consumption of the chickling pea, Lathyrus sativus, and certain related species. Once prevalent throughout Europe, N. Africa, Middle East and parts of the Far East, the disease is presently restricted to India, Bangladesh and Ethiopia. Lathyrism is a form of irreversible, non-progressive spastic paraparesis associated with poorly understood degenerative changes in spinal cord. Domestic animals, notably the horse, also develop hindlimb paralysis after prolonged feeding on lathyrus fodder. Experimental animal models of lathyrism have been reported but none has been satisfactorily investigated, and concurrence between these experimental diseases and the human condition is unproven. The culpable agent in lathyrus species that precipitates paralysis also is unknown. Current attention is focused on the glutamate analog, beta-(N)-oxalyl-amino-L-alanine acid (BOAA). While this compound is present in those lathyrus species that induce spastic paraparesis and, in large doses, reportedly causes neuropathological changes similar to glutamate neurotoxicity, there is little to compare these neuropathological changes with those found in human lathyrism. Chronic primate feeding studies utilizing BOAA need to be carried out to determine whether this agent is responsible for human lathyrism. Some species of lathyrus, notably Lathyrus odoratus, are unable to induce human lathyrism but contain a compound, beta-aminopropionitrile (BAPN), that induces pathological changes in bone ("osteolathyrism") and blood vessels ("angiolathyrism") of experimental animals without damaging the nervous system. However, related compounds, dimethylaminopropionitrile (DMAPN) and beta, beta'-iminodipropionitrile (IDPN), are chronic neurotoxins in humans and animals, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[Structuro-functional properties of the bacteria Bacillus brevis in relation to the accumulation of gramicidin S in cells]

The culture of Bacillus brevis var. G-B R-form was grown in the presence of beta-phenyl-beta-alanine, the inhibitor of gramicidin S synthesis, is characterized by enhanced endogenous respiration and the DPI-reductase activity as compared to the culture synthezising antibiotic. The increased synthesis of the antibiotic in the region of the culture transition from the logarithmic growth phase to the linear one is associated with a decrease in the number of viable cells despite the fact that the culture on the whole does not die but continues to grow. The membranes prepared from young gramicidin S-free cells and from the cells enriched with the antibiotic possess identical electron micrograph images, IR spectra and protein sets as determined by polyacrylamide gel electrophoresis in a Na-DS system. However, in young cell membranes NADH and succinate dehydrogenase are insensitive to gramicidin S and only malate dehydrogenase is inhibited by this antibiotic. In aged cell membranes the activities of all mentioned dehydrogenases are suppressed. Malate dehydrogenase from young cells is weakly inhibited by thyrotrycin obtained from Bac. brevis ATCC 10068; succinate dehydrogenase is entirely insensitive to this antibiotic, while NADH-dehydrogenase is almost completely inhibited by it. The specificity of action on the respiratory chain of peptide antibiotics synthesized by the cells of one strain of Bac. brevis is suggestive of a possible regulatory role of these peptides in the metabolism of the producent. Hence the accumulation of gramicidin S which is adsorbed on the membrane and destroys the respiratory chain function to the cause of the low rate of oxygen uptake by the culture of Bac. brevis var. G-B R-form and of the low activities of DPI-reductases.

2 Methylene-beta-alanine methyl ester: a toxic amino acid originating from the sponge Fasciospongia cavernosa

N-acyl-2-methylene-beta-alanine methyl esters (A) are the main lipidic compounds in the sponge Fasciospongia cavernosa. These compounds were isolated and after methanolysis--2 methylene-beta-alanine methyl esters (AA) and free fatty acid methyl esters were obtained. The interaction of A and AA with the thiol group of cysteine was detected by Ellman's procedure. Both A and AA interact with the thiol group of cysteine in the pH range of 6.0-8.0. Both compounds were found to be strong inhibitors of glyceraldehyde triphosphate dehydrogenase (TPD) from rabbit muscle. The inhibitory effect of A and AA decreases upon addition of beef extract and other protein mixtures containing thiol groups. E. coli growth on a synthetic medium was inhibited by compound AA. Resistant E. coli varieties were isolated by techniques of enrichment cultures. Some of these resistant varieties were shown, by cross-feeding with cysteine dependent E. coli varieties, to excrete cysteine and cysteine derivatives.

3-Chloro-D-alanine chloride-lyase (deaminating) of Pseudomonas putida CR 1.1. Purification and characterization of a novel enzyme occurring in 3-chloro-D-alanine-resistant pseudomonads

A novel enzyme catalyzing cleavage of 3-chloro-D-alanine to pyruvate, ammonia, and chloride ion is distributed in some pseudomonads which have a resistance to high concentrations of 3-chloro-D-alanine. Pseudomonas putida CR 1-1 (AKU 867) was found to have the highest activity of enzyme, which was inducibly formed by the addition of 3-chloro-D-alanine to the medium. The enzyme, tentatively called 3-chloro-D-alanine chloride-lyase, was purified from P.l putida CR 1-1 in seven steps. After the last step, the enzyme appeared to be homogeneous by the criteria of polyacrylamide gel electrophoresis, analytical ultracentrifuge, and double diffusion in agarose. The enzyme has a molecular weight of about 76,000 and consists of two subunits identical in molecular weight (approximately 38,000). The enzyme exhibits absorption maxima at 278 nm and 418 nm, which are independent of the pH (6.0-9.0), and contains 2 mol of pyridoxal 5'-phosphate/mol of the enzyme. The holoenzyme is resolved to the apoenzyme by incubation with phenylhydrazine and reconstituted by the addition of pyridoxal-P. The apoenzyme can be crystallized by adding ammonium sulfate. 3-Chloro-D-alanine chloride-lyase catalyzes an alpha, beta-elimination reaction of 3-chloro-D-alanine and also, but to a lesser extent, D-cysteine and D-cysteine. The enzyme also catalyzes a beta-replacement reaction of chlorine of 3-chloro-D-alanine with hydrosulfide to yield D-cysteine. The important role of this novel beta-lyase enzyme in the detoxication of e-chloro-D-alanine by P. putida CR 1-1 is also discussed.