Dephosphorylation of distinct sites on the 20 kDa myosin light chain by smooth muscle myosin phosphatase.
The dephosphorylation of the myosin light chain kinase and protein kinase C sites on the 20 kDa myosin light chain by myosin phosphatase was investigated. The myosin phosphatase holoenzyme and catalytic subunit, dephosphorylated Ser-19, Thr-18 and Thr-9, but not Ser-1/Ser-2. The role of noncatalytic subunits in myosin phosphatase was to activate the phosphatase activity. For Ser-19 and Thr-18, this was due to a decrease in Km and an increase in k(cat) and for Thr-9 to a decrease in Km. Thus, the distinction between the various sites is a property of the catalytic subunit.
Feng
J
J
First Department of Internal Medicine, Mie University School of Medicine, Tsu, Japan.
Ito
M
M
Nishikawa
M
M
Okinaka
T
T
Isaka
N
N
Hartshorne
D J
DJ
Nakano
T
T
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002645:Chickens; D006801:Humans; D009130:Muscle, Smooth / Q000201:enzymology; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism
D018994:Myosin Light Chains; D011493:Protein Kinase C; D009219:Myosin-Light-Chain Kinase; D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase