Characterization of enzymes involved in the interconversions of different forms of vitamin B6 in tobacco leaves

There are six different vitamin B₆ (VB₆) forms, pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxal 5′-phosphate (PLP), pyridoxamine 5′-phosphate (PMP) and pyridoxine 5′-phosphate (PNP). PLP is a coenzyme required by more than 100 cellular enzymes. In spite of the importance of this vitami...

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Bibliographic Details
Published in:Plant physiology and biochemistry Vol. 49; no. 11; pp. 1299 - 1305
Main Authors: Huang, ShuoHao, Zeng, HaiBin, Zhang, JianYun, Wei, Shu, Huang, LongQuan
Format: Journal Article
Language:English
Published: Paris Elsevier 01.11.2011
Subjects:
Biological and medical sciences
crude protein
Fundamental and applied biological sciences. Psychology
heat
high performance liquid chromatography
metabolism
oxidoreductases
plant physiology
Plant physiology and development
pyridoxal
pyridoxamine
pyridoxine
tobacco
Interconversion
Enzyme activity
Enzyme
HPLC chromatography
Stimulant plant
Plant leaf
Pyridoxine
Metabolism
Nicotiana tabacum
High-performance liquid chromatography
Characterization
Enzymatic activity
Plant physiology
Dicotyledones
Vitamin B
Angiospermae
Spermatophyta
Metabolic conversion
Solanaceae
ISSN:0981-9428
Online Access:Get full text
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Summary:There are six different vitamin B₆ (VB₆) forms, pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxal 5′-phosphate (PLP), pyridoxamine 5′-phosphate (PMP) and pyridoxine 5′-phosphate (PNP). PLP is a coenzyme required by more than 100 cellular enzymes. In spite of the importance of this vitamin, the understanding of VB₆ metabolic conversion in plants is limited. In this study, we developed a sensitive and reliable method to assay VB₆-metabolizing enzyme activities by monitoring their products visually using high-performance liquid chromatography. With this method, the reactions catalyzed by PL/PM/PN kinase, PMP/PNP oxidase, PM-pyruvate aminotransferase, PL reductase and PLP phosphatase were all nicely detected using crude protein extracts of tobacco leaves. Under optimal in vitro conditions, specific activities of those enzymes were 0.15 ± 0.03, 0.10 ± 0.03, 0.08 ± 0.02, 0.64 ± 0.13 and 23.08 ± 1.98 nmol product/min/mg protein, respectively. This is the first report on the conversion between PM and PL catalyzed by PM-pyruvate aminotransferase in plants. Furthermore, the PL reductase activity was found to be heat inducible. Our study sheds light on the VB₆ metabolism taking place in plants.
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ISSN:0981-9428
DOI:10.1016/j.plaphy.2011.08.008