S-Adenosylmethionine synthetase from Escherichia coli is rapidly inactivated by N-ethylmaleimide. In the presence of excess N-ethylmaleimide inactivation follows pseudo first-order kinetics, and loss of enzyme activity correlates with the incorporation of 2 eq of N-[ethyl-2-3H]maleimide/subunit. Preincubation of the enzyme with methionine and the ATP analog adenylylimidodiphosphate reduced the ...

1. The reaction between ferricyanide and egg albumin in solutions of urea, guanidine hydrochloride, and Duponol has been investigated. 2. In neutral medium ferricyanide oxidizes all the SH groups of egg albumin that give a color reaction with nitroprusside. In neutral medium ferricyanide appears to react only with the SH groups of egg albumin. The quantity of ferrocyanide formed can accordingly...

1. Dialysis of a hemoglobin solution against slightly alkaline buffer (pH 8.68) causes a decrease in heme-heme interaction. The value of n in Hill's equation drops from 2.9 to 2.0, while the oxygen affinity increases slightly. Addition of glutathione largely reverses the effects of dialysis (n rises from 2.0 to 2.5 to 2.6). 2. Addition of the sulfhydryl reagent, p-chloromercuribenzoate (1.8 x 1...

Many structurally diverse chemicals (e.g., acrylamide, 2,4dithiobiuret, methylmercury) are electrophiles and cause synaptic dysfunction by unknown mechanisms. The purpose of this Forum review is to discuss the possibility that highly nucleophilic cysteine thiolate groups within catalytic triads of synaptic proteins represent specific and necessary targets for electrophilic neurotoxicants. Most ...

Studies of isolated intact spinach (Spinacia oleracea L.) chloroplasts reveal that most of the available sulfhydryl groups are associated with stromal protein as opposed to a thylakoid membrane fraction under non-denaturing conditions. Increases in sulfhydryl content of approximately 50% occurred with illumination and could be correlated kinetically with a reductive activation of fructose-1,6-b...

For a number of years the view has been widely held that sulfur compounds are concerned in some manner with the production of tumors by aromatic carcinogens. The best known effect of simple polycyclic hydrocarbons upon sulfur metabolism is the formation of mercapturic acids. Since previous in vestigations in this laboratory (8, 9) have shown that mercapturic acids are not present in the urine a...

The effect of cupric ions on the activity, fluorescence, and absorbance, and on the sulfhydryl and flavin adenine dinucleotide contents, of lipoyl dehydrogenase has been examined. The changes take place in two phases during the reaction of the enzyme with copper ions. In the first phase, the lipoic activity of the enzyme decreases to about 10% of its initial value, while its diaphorase activity...

The mechanism by which nitrite inhibits outgrowing spores of Bacillus cereus T was examined by using techniques developed earlier for nitrite analogs. The morphological stage of inhibition, cooperativity effects, effect of pH on inhibition, kinetics of protection against iodoacetate incorporation into membrane sulfhydryl groups, and protection against the bacteriocidal effect of carboxymethylat...

Disc electrophoresis was used to separate water soluble proteins from hardy, non-hardy, and frost killed cabbage (Brassica oleracea var. capitata) leaves. Amidoschwarz staining failed to reveal any new bands as a result of hardening although the relative amounts of proteins in individual bands changed. Sulfhydryl groups in the protein bands were stained with 2,2-dihydroxy-6,6-dinaphthyl disulfi...

The kinetics of the alkylation of the essential sulfhydryl group of papain with chloroacetic acid was studied. The variation of the second order rate constant with pH at 4.5” and 30.5’, r/2 = 0.07, is bell-shaped, with rate constants at a maximum near neutrality, approaching zero at low pH, and approaching a positive minimum at high pH. These profiles are described by a formulation which relate...