Transient Activation of Dihydropteridine Reductase by Ca^<2+>-activated Proteolysis(Biochemistry)

概要

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A transient activation of dihydropteridine reductase (DHPR), which is the regenerating enzyme of tetrahydrobiopterin in the system of aromatic amino acid hydroxylases, was studied during the incubation of DHPR with Ca^<2+>-activated protease, m-calpain. The DHPR subunit (29 k) was cleaved by m-calpain just before the 35th (Ser) and 48th (Val) residue from the N-terminus, generating two new fragments of 21 k and 19 k. By determining kinetic parameters, we found that 21 k and 19 k were more active than the native enzyme and that the activation of them was more remarkable and transient against the natural substrate of quinonoid dihydrobiopterin than against a synthesized substrate. Phosphorylation of DHPR by Ca^<2+>/calmodulin-dependent protein kinase II controlled the sensitivity of the enzyme to the Ca^<2+>- activated protease.
社団法人日本動物学会の論文
2000-05-20