Monoclonal antibody recognition of two subtype forms of protein kinase C in human platelets

Using a hydroxylapatite column chromatographic technique, we obtained the evidence for two subtype forms of protein kinase C in human platelets. These subtypes had a similar chromatographic property to Type II, Type III protein kinase C from the rabbit brain. In addition, in monoclonal antibodies (MC-1a, 2a, 3a) (1) which reacted with specifically Type I, II, III rabbit brain protein kinase C, respectively, only MC-2a and MC-3a reacted with human platelet protein kinase C. All these brain and platelet subtypes have a similar Km value for ATP, the range being from 8.0 to 20.0 microM and a similar IC50 value with regard to the effect of the protein kinase C inhibitor, H-7. Thus, the possibility that specific functions of platelet may be derived from a deficiency of Type I protein kinase C warrants attention.