Partial purification of gamma-glutamyltransferase from human brain microvessels

Two forms of gamma-glutamyltransferase from human brain cortex microvessels were partially purified by gel permeation and ion-exchange and group-affinity chromatography. The specific activity of the purified preparations was 320-fold (detergent form) and 830-fold (proteolytic form) higher than that of the enzyme in the brain cortex homogenate. The relative molecular mass of the proteolytic form of the enzyme was about 90,000 as determined by gel permeation chromatography. The major part of the enzyme (about 80%) was absorbed on Con A-Sepharose 4B. The pH optima for transfer reactions with gamma-glutamyl-4-nitroanilide as donor and glycylglycine and L-cystine as acceptors were in the range of 8.2 to 9.0. The studied enzyme was inhibited by a mixture of L-serine and borate and by bromcresol green.