Isoenzymes of protein kinase C in rat mammary tissue: changes in properties and relative amounts during pregnancy and lactation.
Protein kinase isoenzymes belonging to the protein kinase C (PK-C) family present in rat mammary tissue have been resolved from one another by chromatography on hydroxyapatite, and characterized. PK-C alpha is the predominant isoenzyme and is present at a constant level of activity throughout mammary-gland development and differentiation. In contrast, marked changes in the relative abundance of other mammary PK-C isoenzymes accompany the transition from pregnancy to lactation. The sensitivity of mammary PK-C alpha to Ca2+ is greater in tissue from pregnant than from lactating rats. This isoenzyme has other atypical properties consistent with its being more highly phosphorylated than PK-C alpha in rat brain and spleen. One of the protein kinase isoenzymes resolved from mammary tissue recognizes the peptide substrate used to assay AMP-activated kinase and may thus interfere in the determination of this activity. Another is fully active in the absence of Ca2+ and is more than 80% active in the absence of added lipid effectors. A 'housekeeping' role is proposed for PK-C alpha in mammary tissue, whereas the less abundant PK-C isoenzymes may be involved in mammary cell proliferation and differentiation.
Connor
K
K
Hannah Research Institute, Ayr, Scotland, U.K.
Clegg
R A
RA
D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology; D005260:Female; D007527:Isoenzymes / Q000378:metabolism*; D007774:Lactation / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000201:enzymology*; D008970:Molecular Weight; D010766:Phosphorylation; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000201:enzymology
D007527:Isoenzymes; D011493:Protein Kinase C; D002118:Calcium