probing the active site of rhodanese with disulfide reagents

PROBING THE ACTIVE SITE OF RHODANESE WITH DISULFIDE REAGENTS

Studies on the active site of rhodanese.

The complete loss of enzymic activity on reaction with alkylating agents, aromatic nitro compounds, or aliphatic mercaptans indicates the importance of sulfhydryl groups for catalysis. Analyses during the course of inactivation with any of these reagents revealed the loss of one of the two -SH groups in the rhodanese monomer when inactivation was complete. Amino acid analysis of iodoacetate-ina...

Active site structural features for chemically modified forms of rhodanese.

In the course of the reaction catalyzed by rhodanese, the enzyme cycles between two catalytic intermediates, the sulfur-free and the sulfur-substituted (persulfide-containing) forms. The crystal structure of sulfur-free rhodanese, which was prepared in solution and then crystallized, is highly similar to that of sulfur-substituted enzyme. The inactivation of sulfur-free rhodanese with a small m...

The reaction of choline acetyltransferase with sulfhydryl reagents. Methoxycarbonyl-CoA disulfide as an active site-directed reagent.

The reaction of choline acetyltransferase with methoxycarbonyl alkyl disulfides leads to a progressive loss in enzyme activity as the size of the alkyl group increases from methyl to n-butyl. Reaction with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) or methoxycarbonyl coenzyme A (CoA) disulfide, leads to a total loss of enzyme activity. DTNB inactivation is biphasic (k1 = approximately 9 x 10(2)...

Characterization of rhodanese-tetracyanonickelate. An active site complex that slows sulfur-free rhodanese conversion to inert conformers.

The structure of the rhodanese-tetracyanonickelate (E X Ni(CN)2-4) complex has been characterized here in spectral and physical studies using urea as a structural perturbant. UV difference absorption, sedimentation velocity ultracentrifugation, fluorescence, and circular dichroism data show no significant conformational differences between sulfur-free rhodanese (E) and the E X Ni(CN)2-4 complex...

Probing the active site of liver alcohol dehydrogenase.

site for GSH has been assumed, there is no compelling evidence for the existence of ceoperativity between the subunits of the enzyme. The examples presented show that rate behaviour with regulatory properties can be realized without any assumptions of co-operative subunit interactions. Whether COoperativity indeed is operative in these enzymes remains to be established by the study of ligand bi...