Evidence for a latent form of protein phosphatase 1 associated with cardiac myofibrils.
Detergent-purified myofibrils from bovine heart contained very little spontaneously active protein phosphatase 1 activity. Phosphatase 1, extracted from the myofibrils by freeze-thawing in the presence of 500 mM KCl, was markedly activated by cobalt/trypsin treatment. Myofibril phosphatase 1 was separated from phosphatase 2A by chromatography on heparin-Sepharose. The phosphatase 1 was isolated in a latent form. Pretreatment with trypsin released free catalytic subunit and increased activity about 25-fold. Addition of cobalt with the trypsin increased activity another 2-fold. The latent myofibril phosphatase 1 did not appear to be the same as previously characterized forms of protein phosphatase 1. We suggest that cardiac myofibril phosphatase 1 contains a unique inhibitory subunit which directs the enzyme to the myofibril and regulates the dephosphorylation of myofibril phosphoproteins.
Schlender
K K
KK
Department of Pharmacology, Medical College of Ohio, Toledo 43699.
Wang
W
W
Wilson
S E
SE
D000818:Animals; D002417:Cattle; D002845:Chromatography; D003035:Cobalt / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005615:Freezing; D006358:Hot Temperature; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology* / Q000648:ultrastructure; D009210:Myofibrils / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011189:Potassium Chloride / Q000494:pharmacology; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D011817:Rabbits; D014357:Trypsin / Q000494:pharmacology
D003035:Cobalt; D011189:Potassium Chloride; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D014357:Trypsin