Biochemical characterization of the minor immunophilins

Objective: We present biochemical characterization of the previously descri bed 14 kDa, 37 kDa, and 52 kDa immunophilins and a newly identified 5-8 kDa immunophilin. Design and methods: Proteins were tested for the following enzymatic activi ties-rotamase, G3PDH, protein kinase C, cAMP dependent protein kinase-and f or the ability to inhibit calcineurin phosphatase when complexed with tacro limus (FK506). Results: The 5-8 kDa protein, like the other minor immunophilins, lacks rot amase activity. Since the 37 kDa possesses G3PDH activity, the 5-8 kDa prot ein, 14 kDa protein, and 52 kDa protein were all tested and found to lack G 3PDH activity. Additional work shows that none of the minor immunophilins p ossess protein kinase C or cyclic AMP-dependent protein kinase activity and that the 37 kDa and 5-8 kDa and probably the 52 kDa proteins are capable o f inhibiting calcineurin phosphatase when bound to tacrolimus. Copyright (C ) 2000 The Canadian Society of Clinical Chemists.