title: Bovine lens leucine aminopeptidase. A study of possible roles for the thiol groups in holo- and apoenzyme.
abstract: The apoenzyme of leucine aminopeptidase has to be prepared either under inert conditions or in the presence of 2-thioethanol. Due to the removal of essential zinc ions, buried -SH groups are exposed. These -SH groups show a higher reactivity than the six -SH groups accessible in the native zinc enzyme. During the incubation of the zinc enzyme with guanidine hydrochloride, up to 36 -SH groups are titratble in dependence on the concentration of guanidine hydrochloride. The -SH groups can be distinguished by their reactivity towards Ellman's reagent and can be differentiated into four classes with respect to their function.
mesh_terms: D000818:Animals; D001051:Apoenzymes; D001665:Binding Sites; D002417:Cattle; D004228:Dithionitrobenzoic Acid; D006146:Guanidines; D007700:Kinetics; D007908:Lens, Crystalline / Q000201:enzymology*; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D013438:Sulfhydryl Compounds / Q000032:analysis; D015032:Zinc / Q000032:analysis
chemical_list: D001051:Apoenzymes; D006146:Guanidines; D013438:Sulfhydryl Compounds; D004228:Dithionitrobenzoic Acid; D007931:Leucyl Aminopeptidase; D015032:Zinc