Isolation and purification of tyrosine hydroxylase from callus cultures of Portulaca grandiflora |
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Authors: | Yamamoto Ki Kobayashi N Yoshitama K Teramoto S Komamine A |
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Affiliation: | Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto, 860-8555 Japan. |
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Abstract: | Tyrosine hydroxylase was separated from polyphenol oxidase activity and was highly purified from betacyanin producing callus cultures of Portulaca grandiflora. The purified enzyme catalyzed the formation of DOPA (L-3,4-dihydroxyphenylalanine) from tyrosine and required the pterin compounds (6-methyl-5,6,7,8-tetrahydropterin; 5,6,7,8-tetrahydrobiopterin; 6,7-dimethyl-5,6,7,8-tetrahydropterin) as coenzyme. The K(m) values for tyrosine and 6-methyl-5,6,7,8-tetrahydropterin were 0.5 mM and 0.15 mM, respectively. This enzyme was activated by Fe(2+) and Mn(2+), and inhibited by metal chelating agents. |
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