Metabolism of hydroxypyruvate in a mutant of barley lacking NADH-dependent hydroxypyruvate reductase, an important photorespiratory enzyme activity

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.91.1.395· OSTI ID:5914625

Murray, A J.S.; Blackwell, R D; Lea, P J ^[1]

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1. Univ. of Lancaster (England)

A mutant of barley (Hordeum vulgare L.), LaPr 88/29, deficient in NADH-dependent hydroxypyruvate reductase (HPR) activity has been isolated. The activities of both NADH (5%) and NADPH-dependent (19%) HPR were severely reduced in this mutant compared to the wild type. Although lacking an enzyme in the main carbon pathway of photorespiration, this mutant was capable of CO{sub 2} fixation rates equivalent to 75% of that of the wild type, in normal atmospheres and 50% O{sub 2}. There also appeared to be little disruption to the photorespiratory metabolism as ammonia release, CO{sub 2} efflux and {sup 14}CO{sub 2} release from L-(U-{sup 14}C)serine feeding were similar in both mutant and wild-type leaves. When leaves of LaPr 88/29 were fed either ({sup 14}C)serine or {sup 14}CO{sub 2}, the accumulation of radioactivity was in serine and not in hydroxypyruvate, although the mutant was still able to metabolize over 25% of the supplied ({sup 14}C)serine into sucrose. After 3 hours in air the soluble amino acid pool was almost totally dominated by serine and glycine. LaPr 88/29 has also been used to show that NADH-glyoxylate reductase and NADH-HPR are probably not catalyzed by the same enzyme in barley and that over 80% of the NADPH-dependent HPR activity is due to the NADH-dependent enzyme. We also suggest that the alternative NADPH activity can metabolize a proportion, but not all, of the hydroxypyruvate produced during photorespiration and may thus form a useful backup to the NADH-dependent enzyme under conditions of maximal photorespiration.

• OSTI ID: 5914625
• Journal Information: Plant Physiology; (USA), Journal Name: Plant Physiology; (USA) Vol. 91:1; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BARLEY
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CEREALS
ENZYME ACTIVITY
ENZYMES
GRASS
ISOTOPE APPLICATIONS
KETO ACIDS
LABELLED COMPOUNDS
LILIOPSIDA
MAGNOLIOPHYTA
METABOLISM
MUTANTS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PLANTS
PYRUVIC ACID
TRACER TECHNIQUES