Differential solubilization of rabbit liver plasma membrane gamma-glutamyltransferase by proteases and detergents: effect of phenobarbital treatment

Abstract

In an attempt to understand the mechanism of gamma-glutamyltransferase transfer from the liver to the plasma, potassium chloride, sodium dodecyl sulfate and proteases (papain and bromelain) were used to solubilize rabbit liver plasma membrane gamma-glutamyltransferase. Potassium chloride solutions solubilized 10-30% of membrane proteins but only 1-3% of membrane gamma-glutamyltransferase activity. However, when sodium dodecyl sulfate is used, even at low concentration (0.1-0.2%, w/v) greater than 90% of membrane gamma-glutamyltransferase activity and about 80% of membrane proteins can be solubilized. Furthermore, we showed that unlike the effect of bile salts on the membrane gamma-glutamyltransferase of phenobarbital-treated animals, the same treatment seems to have no influence on membrane gamma-glutamyltransferase solubilization by proteases. Indeed, the ratios of gamma-glutamyltransferase solubilization by papain or bromelain were the same for liver membranes obtained from control and phenobarbital-treated animals.