Monkey Glutathione S-Aryltransferases

Abstract
The molecular and enzymatic properties of the major component (Fraction IV) of glutathione S-aryltransferases [EC 2.5.1.13] purified from the liver of monkey (mainly rhesus monkey) have been investigated. The enzyme had a molecular weight of about 48,000 and was composed of two subunits of apparently identical molecular weight (ca. 24,000) bound to each other non-covalently. Each subunit contained one SH group. The amino acid composition showed characteristic high contents of leucine and glutamic acid residues. No amino-terminal residue was detected by the dansyl method. The enzyme showed a rather broad optimum pH range from 7.5 to 9 with 1,2-dichloro-4-nitrobenzene as a substrate. It was moderately stable below 40°C at pH 7.5. However, it showed an anomalous instability at pH around 4.2. It was reversibly denatured at least partially by urea or guanidine hydrochloride and irreversibly denatured by sodium dodecylsulfate. It was significantly inhibited by Zn2+, Cd2+ and Hg2+, and also by benzene hexachloride. It was extensively inactivated by reaction with phenylglyoxal or 2,4,6-trinitrobenzene sulfonate, whereas several SH reagents were without marked effect on the activity under the reaction conditions employed.