The genes encoding the protein kinase C enzymes are widely distributed, e.g., PRKCA on chromosome 17, PRKCB1 on 16, and PRKCG on 19. Although the sequence homology among the PRKC family of genes is extensive, the pattern of expression varies among tissues. For example, the delta polypeptide appears to be the major isoform expressed in mouse hematopoietic cells. Mischak et al. (1991) isolated and characterized the mouse Prkcd gene.Aris et al. (1993) found that PKC-delta underwent calcium-independent autophosphorylation in the presence of phosphatidylserine and diacylglycerol. Diacylglycerol was an absolute requirement for PKC-delta activation. This and other cofactor and substrate requirements distinguished human PKC-delta from its mouse homolog.