Purification and properties of cyclic AMP-dependent protein kinase from rat epididymis

Abstract

Two protein kinases (I and II: EC 2.7.1.37) that show a high degree of substrate specificity for protamine rather than histones, phosvitin and casein were partly purified from rat epididymal tissue. The enzymes were present in the cytosol because greater than 80% of the enzymic activity was recovered in the soluble fraction. The kinases required Mg2+ for activity although Co2+ and Mn2+ were partial substitutes. Zn2+ (1 mM) inhibited nearly completely the activity of the enzymes. Both the kinases showed high affinity for activation with cyclic AMP compared to other cyclic nucleotides. Amino acid analysis of 32P-labelled protamine product revealed that the kinases transfer the terminal phosphate of ATP to serine residues of the protein. The isoenzymes I and II showed certain differences in relation to their hydroxyapatite-chromatography profiles, pH activation profiles, heat sensitivity and Km for ATP and cyclic AMP.

Androgenic control of the cyclic AMP-dependent protein kinase isoenzymes of the rat epididymis

“…So the presence of a cAMP-dependent form cannot be determined by the data in Table 1. However, a study by Biswas & Majumder (1982) …”

“…Activities of the cyclic AMPdependent and -independent protein kinases of the caput epididymidis from immature rats are elevated after testosterone administration (Bernard & Wassermann, 1972) and the ratio of the cyclic AMP-dependent to the cyclic GMP-dependent protein kinases increases during post-natal development (Kuo & Williams, 1979). As in other tissues, the cyclic AMP-dependent protein kinase of the rat epididymis also exists as two isoenzymes, types I and II (Biswas & Majumder, 1982). The isoenzymes differ in charge and can be separated by ion-exchange chromatography.…”

Enzymic characteristics of the isoenzymes of rat epididymal neutral α-mannosidases and their changes during development in vivo

“…By this washing procedure approx. 98% of epididymal fluid was removed from the epididymides (Biswas & Majumder, 1982). The washed tissue was then homogenized in the same buffer (1 g/lOml) and the homogenate was filtered through three layers of cheese-cloth.…”