Aminoacylase from pig kidney contains no disulfide bonds

Both non-reduced/reduced(NR/R)two-dimensional diagonal SDS-PAGE and NR/Rone-dimensional SDS-PAGE showed no disulfide bonds in aminoacylase from pig kidney.Eight andfour thiol groups were modified in the native enzyme by 2-chloromercuri-4-nitrophenol(MNP)andEllman’s reagent,5,5’-dithiobis(2-nitrobenzoic add)(DTNB),and another two and six thiol groupscould be exposed and modified in 7mol/L guanidine hydrochloride,respectively.The enzyme denaturedwith guanidine or urea was found to contain a total of ten thiol groups.This is in good agreement with therecently deduced amino acid sequence from cloned cDNA.It is therefore clear that no disulfide bridges existin aminoacylase from pig kidney.