Showing papers on "Lactoylglutathione lyase published in 1983"

Nonstereospecific substrate usage by glyoxalase I.

Abstract: Glyoxalase I operates on a mixture of rapidly interconverting diasteriomeric thiohemiacetals, formed in a preequilibrium step between glutathione and alpha-ketoaldehyde. That both diasteriomers are directly used as substrates by the enzyme from yeast and from porcine erythrocytes is an outcome of a series of isotope-trapping experiments in which pulse solutions composed of the two diasteriomeric thiohemiacetals, due to [3H]glutathione and phenylglyoxal, are rapidly mixed with chase solutions containing excess unlabeled glutathione and successively increasing concentrations of glyoxalase I. As the enzyme approaches infinite concentration in the chase solution, the radioactivity incorporated into the S-mandeloylglutathione product approaches 100% of the total radioactivity due to both diasteriomers from the pulse solution. The special properties of the active site that allow the enzyme to accommodate both diasteriomeric substrate forms may also account for the fact that the cis and the trans isomers of various para-substituted S-(phenylethenyl)glutathione derivatives are both strong competitive inhibitors of the enzyme. A catalytic mechanism is proposed for glyoxalase I involving catalyzed interconversion of the bound diasteriomeric thiohemiacetals before transformation to final product.

S-carbobenzoxyglutathione: a competitive inhibitor of mammalian glyoxalase II.

Abstract: An effective competitive inhibitor of mammalian glyoxalase II has been synthesized and studied. The compound, S-carbobenzoxyglutathione, is almost totally inactive as an inhibitor of mammalian glyoxalase I. This is in marked contrast to other glyoxalase II competitive inhibitors, which in general are even more effective against glyoxalase I. S-Carbobenzoxyglutathione has found utility as an affinity ligand for the purification of rat liver glyoxalase II, and it may well have use in the study of the glyoxalase enzymes in vivo.

Glyoxalase I in regenerating mouse liver exposed to carcinogens.

Abstract: Glyoxalase I is the first component of glyoxalase system which is involved in detoxification of alpha-ketoaldehydes and converts them to nontoxic substances. This study reports changes in Glyoxalase I activity in relation to DNA synthesis in regenerating liver treated with two polycyclic aromatic hydrocarbons - 7,12-dimethylbenz (a) anthracene and benzo(a)pyrene. Livers after partial hepatectomy show consistent increase in Gly. I which reaches to its peak at 24 hr after surgery. [3H]Thymidine incorporation into DNA also follows the same trend as does Gly. I in regenerating liver. Both the carcinogens have significantly reduced the activity of Gly. I and DNA biosynthesis when compared with untreated partially hepatectomized control livers. The study reveals that though regenerating liver has been considered as an experimental model for neoplasia, unlike tumors (where Gly. I is either absent or in undetectable quantities) it possesses more Gly. I than in normal liver. On the other hand, preneoplastic liver during initiation (in regenerating liver treated with carcinogens, initiation is expected to occur) has very low activity. This suggests that Gly. I is not only involved in controlling growth but possibly is involved in some other phenomenon which is somehow depressed in preneoplastic and cancerous tissues.

Effect of Squaric Acid and Isoascorbate on Glyoxalase-I Cell Division and DNA Synthesis in Datura Callus

Abstract: The presence of the enzyme glyoxalase was reported by Neuberg (1) and Dakin and Dudley in 1913 (2). Since then, it has been isolated from many animal systems and from yeast. However, except for one casual report, its existence has not been reported in higher plants.