On the involvement of intramolecular protein disulfide in the irreversible inactivation of 3-hydroxy-3-methylglutaryl-CoA reductase by diallyl disulfide.
Treatment with diallyl disulfide, a constituent of garlic oil, irreversibly inactivated microsomal and a soluble 50 kDa form of HMG-CoA reductase. No radioactivity was found to be protein-bound on treating the soluble enzyme with [35S]diallyl disulfide, indicating the absence of the mixed disulfide of the type allyl-S-S-protein. SDS-PAGE and Western blot analyses of the diallyl-disulfide-treated protein showed no traces of the dimer of the type protein-S-S-protein, but clearly indicated BME-reversible increased mobility, as expected of an intramolecular protein disulfide. The sulfhydryl groups, as measured by alkylation with iodo[2-14C]acetic acid, were found to decrease in the diallyl-disulfide-treated enzyme protein. Tryptic peptide analysis also gave support for the possible presence of disulfide-containing peptides in such a protein. It appears that diallyl disulfide inactivated HMG-CoA reductase by forming an internal protein disulfide that became inaccessible for reduction by DTT, and thereby retaining the inactive state of the enzyme.
Omkumar
R V
RV
Department of Biochemistry, Indian Institute of Science, Bangalore.
Kadam
S M
SM
Banerji
A
A
Ramasarma
T
T
D000498:Allyl Compounds; D000818:Animals; D004220:Disulfides / Q000737:chemistry / Q000494:pharmacology*; D004229:Dithiothreitol; D004789:Enzyme Activation / Q000187:drug effects; D006903:Hydroxymethylglutaryl CoA Reductases / Q000737:chemistry; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D011487:Protein Conformation; D051381:Rats
D000498:Allyl Compounds; D004220:Disulfides; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; C028009:diallyl disulfide; D006903:Hydroxymethylglutaryl CoA Reductases; D004229:Dithiothreitol