Cellular transglutaminase. The particulate-associated transglutaminase from chondrosarcoma and liver: partial...

A transglutaminase from the malignant chondrocytes, rat swarm chondrosarcoma cells, was partially purified and characterized in an effort to understand transformation-induced changes in its activity. This enzyme separated by DE52 column chromatography after extraction from the particulate fraction of cell lysate was found to be distinct from previously characterized transglutaminases in its electrophoretic mobility, molecular size, substrate specificity, and immunologic reactivity. This enzyme was identified as a transglutaminase by its catalysis of amine (putrescine, spermine) incorporation at the carboxamide group of protein-bound gamma-glutamyl residues, and accordance of its kinetic data with the modified double displacement mechanism described for other transglutaminases. Limited proteolysis of the isolated enzyme resulted in a 3-4-fold increase of catalytic activity and a concomitant reduction of molecular size by approximately one-half. Incubation of labeled amine with chondrosarcoma cell lysate resulted in labeling of only a few proteins that appeared to be extensively cross-linked and that were located mostly in the particulate fraction of the cells. Transglutaminase extracted from the rat liver particulate fraction displayed enzymatic and structural properties closely resembling those of the enzyme from chondrosarcoma cells.