title: Isolation and purification of tyrosine hydroxylase from callus cultures of Portulaca grandiflora.
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.
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto, 860-8555 Japan.
authors.lastname: Yamamoto Ki
authors.forename: N
authors.initials: N
authors.lastname: Kobayashi
authors.forename: K
authors.initials: K
authors.lastname: Yoshitama
authors.forename: S
authors.initials: S
authors.lastname: Teramoto
authors.forename: A
authors.initials: A
authors.lastname: Komamine
mesh_terms: D002384:Catalysis; D004156:Catechol Oxidase / Q000737:chemistry / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003067:Coenzymes / Q000494:pharmacology; D046508:Culture Techniques; D004295:Dihydroxyphenylalanine / Q000096:biosynthesis; D007501:Iron / Q000494:pharmacology; D007700:Kinetics; D019684:Magnoliopsida / Q000737:chemistry / Q000201:enzymology*; D008345:Manganese / Q000494:pharmacology; D011622:Pterins / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D003067:Coenzymes; D011622:Pterins; D014443:Tyrosine; D008345:Manganese; D004295:Dihydroxyphenylalanine; D007501:Iron; D004156:Catechol Oxidase; D014446:Tyrosine 3-Monooxygenase