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At least 37 records · Page 2Linked to original sources
PubMed1978

Possible role of gamma-aminobutyric acid synthesis in the mechanism of dexamethasone feedback action.

Specific inhibition of glutamic acid decarboxylase (GAD, EC 4.1.1.15; the main enzyme involved in the synthesis of gamma-aminobutyric acid) by mercaptopropionic acid interferes with the effect of dexamethasone on both the resting and stress-induced secretion of ACTH. It is postulated that dexamethasone may, at least in part, inhibit the secretion of ACTH via the induction of GAD, thereby raising the level of gamma-aminobutyric acid in the central nervous system.

3-Mercaptopropionic Acid↗
PubMed1978

The anticonvulsant action of L-2,4-diaminobutyric acid.

The GABA uptake inhibitor, L-2,4-diaminobutyric acid (L-DABA) was examined for potential anticonvulsant activity in mice. Given intracerebroventricularly (i.c.v., 2 mumoles) L-DABA almost doubled the CD50 of picrotoxin and 3-mercaptopropionate (3-MP), a glutamate decarboxylase inhibitor--the convulsants being administered 15 min after the L-DABA. The anticonvulsant effect was not observed after 40 min. L-DABA given i.p (5 mmoles/kg) was also anticonvulsant against 3-MP but given i.p. or i.c.v. had no anticonvulsant action against strychnine. The D-isomer of DABA, less active as an inhibitor of GABA uptake, had no anticonvulsant activity against 3-MP and nor did three other inhibitors of GABA uptake, namely nipecotic acid, cis-1,3-aminocyclohexane carboxylic acid (ACHA) and beta-alanine. Possible mechanisms of the anticonvulsant action of L-DABA are discussed.

3-Mercaptopropionic Acid↗
PubMed1979

Design of potent and specific inhibitors of carboxypeptidases A and B.

The combination in one molecule of functional groups that can interact specifically with different substrate binding areas at the active site of carboxypeptidases A and B has led to the development of potent and specific inhibitors of these enzymes. 2-Benzyl-3-mercaptopropanoic acid (SQ 14,603) has a Ki of 1.1 x 10(-8) M vs. carboxypeptidase A and a Ki of 1.6 x 10(-4) M vs. the B enzyme. 2-Mercaptomethyl-5-guanidinopentanoic acid (SQ 24,798) has a Ki of 4 x 10(-10) M vs. carboxypeptidase B and a Ki of 1.2 x 10(-5) M vs. carboxypeptidase A. It is proposed that the sulfhydryl groups of these inhibitors bind to the catalytically important zinc ions of these enzymes, and that, in conjunction with the benzyl and guanidinopropyl side chains, they are responsible for their specificity.

3-Mercaptopropionic Acid↗
PubMed1979

Potentiating mechanism of bradykinin action on smooth muscle by sulfhydryl compounds.

(4R)-3-[(2S)-3-Mercapto-2-methylpropanoyl]-4-thiazolidinecarboxylic acid (YS-980), a potent angiotensin I (AI) converting enzyme inhibitor, inhibited the contractile response of isolated guinea-pig ileum to AI but not to AII, while it potentiated the response to bradykinin. Other sulfhydryl compuonds also produced inhibition of AI action, and the effects were closely correlated with their potentiating activities against bradykinin action. These results suggest that it is mainly inhibition of the enzyme in the tissue which participates in the mechanism of potentiation of kinin action by YS-980.

3-Mercaptopropionic Acid↗
PubMed1992

Bradykinin degrading activity in cultured human endothelial cells.

The role of angiotensin-converting enzyme (ACE), neutral endopeptidase 24.11 (NEP), and other peptidases in the endothelial degradation of bradykinin was investigated in cultured human umbilical vein endothelial cells (HUVEC). The major part of the kininase II activity on intact cells was attributed to ACE activity, the minor part to NEP activity. Amastatin, as aminopeptidase inhibitor, and DL-2-mercaptomethyl-3-guanidinoethyl-thiopropionic acid (MGTA), an inhibitor of kininase I, did not affect endothelial kininase activity. The decline of the bradykinin concentrations in the supernatant of intact endothelial monolayer indicated a total kininase activity of 289 +/- 27 fmol/min/dish. The calculated activity of ACE was 223 fmol/min/dish and the neutral endopeptidase activity was 51 fmol/min/dish. Thus, ACE and neutral endopeptidase are the main kininases in the degradation of bradykinin by intact endothelial cells. In contrast to the intact endothelial monolayers, in homogenates additional kininase activity was found which was not affected by either ACE and NEP inhibitors nor by amastatin and MGTA.

3-Mercaptopropionic Acid↗
PubMed1979

The convulsant drugs 3-mercaptopropionate and methionine sulfoximine inhibit L-glutamate and L-aspartate binding to a hydrophobic protein fraction from rat cerebral cortex.

The action of the convulsant drugs, methionine sulfoximine (MSO), 3-mercaptopropionate (3-MP), megimide (MG), and allylglycine on the binding of L-[14C]aspartate, L-[14C]glutamate and [14C]GABA to a hydrophobic protein fraction isolated from rat cerebral cortex was studied. Using the convulsant at 10(-4) M concentration and the radioactive ligands as 10(-6) M the binding of L-[14C]glutamate was inhibited 60% by 3-MP and 40% by MSO, while MG and allylglycine had no effect. The binding of L-[14C]aspartate was inhibited 55%, and 10--20% by 3-MP and MSO, respectively, while MG and allylglycine had not effect. None of the drugs mentioned, except for a minimal inhibition by MG, altered the binding of [14C]GABA. Neither MSO nor 3-MP affected the high-affinity sites for L-[14C]glutamate of L-[14C]aspartate, but they had a strong inhibitory action on the medium affinity site. These results are discussed in relation to the possible mechanism of action of these drugs on L-glutamate and L-aspartate receptors.

3-Mercaptopropionic Acid↗
PubMed1979

A novel orally active converting-enzyme inhibitor YS 980: effects on blood pressure in spontaneously hypertensive rats.

1. The effects of long-term treatment with the angiotensin I converting-enzyme inhibitor YS 980 were examined in stroke-prone spontaneously hypertensive (sp-SH) rats. Development of hypertension was markedly blunted in the YS 980-treated animals. 2. Effective converting-enzyme inhibition was confirmed by significant increases in plasma angiotensin I (ANG I) and plasma renin concentration, inhibition of the pressor responses to intravenous ANG I and potentiation of the depressor responses to intravenous bradykinin. 3. Urinary free aldosterone excretion was decreased but no changes in urinary sodium and potassium excretion were observed. 4. The pressor responses to intravenous leucine-enkephalin were reduced. 5. The pressor responses to injection of ANG I and bradykinin into the lateral brain ventricle were unaltered. 6. We conclude that the antihypertensive action of YS 980 in sp-SH rats cannot be explained by the inhibition of the plasma renin-angiotensin system alone. Effects on other peptide systems must be considered.

3-Mercaptopropionic Acid↗
PubMed1977

Allergic contact dermatitis to a photopolymerizable resin used in printing.

Organic photopolymerizable resins increasingly used in printing make it possible to produce flexible, lighter plates. A certain number of skin lesions and general symptoms appeared upon manipulation of plates made by the Letterflex process. In the workshop where this study was carried out, 12 out of 15 people suffered various degrees of skin lesions. The epicutaneous tests and biopsies performed indicate an allergic type reaction to one of the resin's constituents, polythiol. Experiments with animals confirm the strong allergenicity of this compound.

3-Mercaptopropionic Acid↗
PubMed1979

Formation of stable anhydrides from CoA transferase and hydroxamic acids.

Acetohydroxamic acid reacts with the enzyme-CoA form of succinyl-CoA:3-ketoacid coenzyme A transferase to give an inactive product with a rate constant of 860 M-1 min-1 at pH 8.1, 25 degrees C. The reaction is reversible in the presence of coenzyme A and has an equilibrium constant of 0.040. The product is an anhydride that is an analog of the intermediate that has been postulated in the normal catalytic pathway; it is inactive because coenzyme A does not react with the acyl group of the hydroxamic acid. The equilibrium constant for formation of the anhydride from the thil ester of enzyme and methyl 3-mercaptopropionate is 75 times larger than the equilibrium constant of 2.2 for the formation of N,O-diacetylhydroxylamine from acetohydroxamic acid and acetyl-CoA. This shows that the enzyme stabilizes the anhydride at the active site by at least -2.6 kcal mol-1. Succinomonohydroxamic acid reacts with enzyme-CoA as both a substrate and an inactivator, with relative rate constants of 25:1. The inactivation is irreversible, indicating that the enzyme provides a larger stabilization of at least -5.9 kcal mol-1 for the anhydride of an analog of the specific substrate, succinate. The results are consistent with the hypothesis that the enzyme stabilizes an anhydride that is formed at the active site during turnover of normal substrates through a stepwise reaction mechanism.

Acetoacetates↗