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Phosphorylation by Ca 2+ /calmodulin‐dependent protein kinase II and protein kinase C of sepiapterin reductase, the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin
Author(s) -
Katoh Setsuko,
Sueoka Terumi,
Yamamoto Yoshimi,
Takahashi Susumu Y.
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)80462-1
Subject(s) - tetrahydrobiopterin , biochemistry , protein kinase a , mitogen activated protein kinase kinase , map2k7 , calmodulin , biology , kinase , enzyme , chemistry , cyclin dependent kinase 2 , microbiology and biotechnology , cofactor
Sepiapterin reductase, the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin, was stoichiometrically phosphorylated by Ca 2+ /calmodulin‐dependent protein kinase II and protein kinase C (Ca 2+ /phospholipid‐dependent protein kinase) in vitro. Maximal incorporation of phosphate into the enzyme subunit by these was 3.05 ± 0.05 ( n = 4) and 0.74 ± 0.03 ( n = 5) 32 P mol per mol enzyme subunit, respectively. The enzyme was not phosphorylated by cyclic nucleotide‐dependent protein kinase of either the cAMP‐dependent or cGMP‐dependent type in this study. Dihydropteridine reductase, another enzyme working in direct supply of tetrahydrobiopterin, was also a good substrate for Ca 2+ /calmodulin‐dependent protein kinase II. Phosphorylation of sepiapterin reductase by these protein kinases modified the kinetic properties of the enzyme. It is likely that these multifunctional Ca 2+ ‐activated protein kinases may play a role in the regulation of the physiological function of the BH4‐generating enzymes in vivo, as was previously found in the case of BH4‐requiring enzymes.