Rat liver was homogenized in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density-gradient centrifugation. Transglutaminase, when assayed with putrescine and dimethylcasein as substrates, showed three distinct localizations, cytosol (73%), plasma membrane (20%), and nuclei (7%). The distribution was unaffected by homogenization in the presence of potassium chloride, indicating that the particulate activity was not due to adsorbed cytosolic enzyme. The specific activity and subcellular distribution of transglutaminase in rats which had received intra-peritoneal glucagon, stimulating endocytosis; or which had been subjected to sub-total hepatectomy 2, 16, or 32 h previously, showed no significant difference from control animals.

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