The mechanism of arginase activation has been widely studied during the past few years. Salaskin and Solowjew (1) and Waldschmidt-Leitz, Schaffner, and Kocholaty (2) believed that sulfhydryl compounds were the specific activators of arginase. This viewpoint was attacked by Edlbacher, Kraus, and Walter (3), and by Klein and Ziese (4), who presented evidence that the effect obtained with sulfhydr...

Peroxynitrite (ONOO-) toxicity is associated with protein oxidation and/or tyrosine nitration, usually resulting in inhibition of enzyme activity. We examined the effect of ONOO- on the activity of purified rat liver microsomal glutathione S-transferase (GST) and found that the activity of reduced glutathione (GSH)-free enzyme was increased 4- to 5-fold by 2 mM ONOO-; only 15% of this increased...

Serine hydroxymethyltransferase from Escherichia coli was purified to homogeneity. The enzyme was a homodimer of identical subunits with a molecular weight of 95,000. The amino acid sequence of the amino and carboxy-terminal ends and the amino acid composition of cysteine-containing tryptic peptides were in agreement with the primary structure proposed for this enzyme from the structure of the ...

The inhibition of human erythrocyte glucose 6-phosphate dehydrogenase (G6PD) by Cd (II), Al (III) and Ni (II) was studied. The enzyme was partially purified having specific activity of 1.4 U/mg protein. Cadmium inhibited G6PD activity progressively up to 1.5 mM concentration where about 65% of the enzyme activity was lost. The inhibition was uncompetitive and noncompetitive with respect to gluc...

Several inhibitors of angiotensin converting enzyme were also found to inhibit aminopeptidase P, whereas inhibitors of other mammalian aminopeptidases were ineffective. Aminopeptidase P purified from pig kidney cortex was found to contain one atom of zinc per polypeptide chain, confirming its metalloenzyme nature. The concentrations of converting enzyme inhibitors required to cause 50% inhibiti...

1. S-Adenosylhomocysteinase (S-adenosylhomocysteine hydrolase, EC 3.3.1.1) was slowly inactivated in the presence of adenine and adenine nucleotides (Ueland & Saebø, 1979b). 2. The enzyme was stabilized by 2-mercaptoethanol and dithiothreitol, and was slowly inactivated at 37 degrees C in the absence of reducing agents and rapidly inactivated in the presence of 5,5'-dithiobis-(2-nitrobenzoic ac...

Carbamyl phosphate synthetase from Escherichia coli, which is composed of a light and a heavy subunit, is inhibited with respect to its glutamine-dependent reactions by treatment with ~-2-amino-4-oxo-5-chloro[5-‘~C]pentanoic acid. This glutamine analog reacts with a glutamineor albizziinprotectable site on the light subunit to yield an enzyme covalently linked to a 4-oxo[W]norvaline moiety. The...

Johnsongrass (Sorghum halepense (L.) Pers.) is sensitive to methanearsonate, foliar application resulting in a topkill. Investigation of the pattern of photosynthesis by radioautography revealed an accumulation of malate in methanearsonate-treated leaves. Accumulation of malate was attributed to an inhibition of NADP(+)-malic enzyme which was found to be sensitive to sulfhydryl group reagents i...

Compounds containing sulfhydryl groups have occupied a unique position in metabolic and chemical studies because of their intimate association with the problems of protein structure (l), enzyme function (2), and cellular proliferation (3). Kolthoff and Harris (4) described an amperometric method for the determination of mercaptans which Benesch and Benesch adapted for use with amino acids and p...

The enzyme xanthine: acceptor oxidoreductase found in rat heart equilibrates between three forms differing in electron acceptor specificity. Form D transfers electrons exclusively to NAD+ and accounts for 85% of total oxidoreductase activity. Form O transfers electrons to molecular oxygen and accounts for 8%. The D/O form prefers NAD+, but without NAD+ transfers electrons to oxygen. Interconver...