GTP hydrolysis by human tissue transglutaminase homologue.

Human tissue transglutaminase homologue cDNA was expressed in E. coli to analyze the catalytic characteristics. The transglutaminase homologue was purified by immunoaffinity chromatography. Specificity of GTP binding by the homologue was demonstrated by photoaffinity labeling in the absence or presence of GTP-gamma-S. The homologue had GTPase activity with an apparent Km value of 1.8 microM, several-fold lower than the reported Km values for the native tissue transglutaminase. GTPase activity was inhibited by guanine nucleotides in order GTP-gamma-S > GDP > GMP. The higher GTPase activity of the homologue may be related to the signaling events function.