Differential expression of cyclic AMP-dependent protein kinase isozymes in normal human melanocytes and malignant melanomas.

Analysis of cyclic AMP-dependent protein kinase catalytic (C) and regulatory (R) subunits in normal human melanocytes and malignant melanomas demonstrated molar excess of regulatory over catalytic subunit in both cell types. Overall, greater catalytic activity, as a measure of C subunit, and cyclic AMP binding activity, as a measure of R subunit, were detected in metastatic compared to primary melanomas compared to normal human melanocytes. The protein kinase-specific R subunits, expressed in both melanocytes and malignant melanomas, were identified as RI-alpha and RII-alpha. Differences were noted for the ratios of RI/RII and RI holoenzyme/free RI subunit among different melanomas.