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Enzymology of L-tyrosine biosynthesis in mung bean (Vigna radiata (L. ) Wilczek)

Journal Article · · Plant Physiol.; (United States)
DOI:https://doi.org/10.1104/pp.64.5.727· OSTI ID:5520106
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The enzymes of the 4-hydroxyphenylpyruvate (prephenate dehydrogenase and 4-hydroxyphenylpyruvate aminotransferase) and pretyrosine (prephenate aminotransferase and pretyrosine dehydrogenase) pathways of L-tyrosine biosynthesis were partially purified from mung bean (Vigna radiata (L.) Wilczek) seedlings. NADP-dependent prephenate dehydrogenase and pretyrosine dehydrogenase activities coeluted from ion exchange, adsorption, and gel-filtration columns, suggesting that a single protein (52,000 daltons) catalyzes both reactions. The ratio of the activities of partially purified prephenate to pretyrosine dehydrogenase was constant during all purification steps as well as after partial inactivation caused by p-hydroxymercuribenzoic acid or heat. The activity of prephenate dehydrogenase, but not of pretyrosine dehydrogenase, was inhibited by L-tyrosine at nonsaturating levels of substrate. The K/sub m/ values for prephenate and pretyrosine were similar, but the specific activity with prephenate was 2.9 times greater than with pretyrosne. Two peaks of aromatic aminotransferase activity utilizing L-glutamate or L-aspartate as amino donors and 4-hydroxyphenylpyruvate, phenylpyruvate, and/or prephenate as keto acid substrates were eluted from DEAE-cellulose. Of the three keto acid substrates, 4-hydroxyphenylpyruvate was preferentially utilized by 4-hydroxyphenylpyruvate aminotransferase whereas prephenate was best utilized by prephenate aminotransferase. The identity of a product of prephenate aminotransferase as pretyrosine following reaction with prephenate was established by thin layer chromatography of the dansyl-derivative.
Research Organization:
State Univ. of New York, Binghamton
DOE Contract Number:
EP-78-S-02-4967
OSTI ID:
5520106
Journal Information:
Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 64:5; ISSN PLPHA
Country of Publication:
United States
Language:
English

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Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
AMINOTRANSFERASES
ASPARTIC ACID
BEANS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBOXYLIC ACIDS
CATALYTIC EFFECTS
CHROMATOGRAPHY
COENZYMES
DEHYDROGENASES
ENZYME ACTIVITY
ENZYMES
FOOD
GLUTAMIC ACID
HYDROXY ACIDS
INHIBITION
KETO ACIDS
KINETICS
MOLECULAR WEIGHT
NADP
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PROTEINS
PURIFICATION
REACTION KINETICS
SEEDLINGS
SEPARATION PROCESSES
SUBSTRATES
SYNTHESIS
TEMPERATURE EFFECTS
TRANSFERASES
TYROSINE
VEGETABLES