Journal Article

Isolation and Purification of Tyrosine Hydroxylase from Callus Cultures of <i>Portulaca grandiflora</i>

Ken-ichi Yamamoto, Naoko Kobayashi, Kunijiro Yoshitama, Susumu Teramoto and Atsushi Komamine

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 9, pages 969-975
Published in print September 2001 | ISSN: 0032-0781
Published online September 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce125
Isolation and Purification of Tyrosine Hydroxylase from Callus Cultures of Portulaca grandiflora

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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 Km 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 Fe2+ and Mn2+, and inhibited by metal chelating agents.

Keywords: Key words: Betacyanin — DOPA — Portulaca grandiflora — Polyphenol oxidase (EC 1.10.3.1) — Pterin — Tyrosine hydroxylase (EC 1.14.16.2).; Abbreviations: BH4, 5,6,7,8-tetrahydrobiopterin; DMPH4, 6,7-dimethyl-5,6,7,8-tetrahydropterin; DOPA, l-3,4-dihydroxyphenylalanine; DTT, dithiothreitol; 6MPH4, 6-methyl-5,6,7,8-tetrahydropterin.

Journal Article.  3293 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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