Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Kleczkowski, Leszek A.; Edwards, Gerald E.

doi:10.1104/pp.91.1.278

Cited by 25 publications

(23 citation statements)

References 36 publications

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“…A similar conclusion had earlier been drawn for maize leaves (6), in contrast with the situation in pea or spinach, where three-fourths to nine-tenths of the glyoxylate reduction appears to be attributable to GR, based on acetohydroxamate sensitivity (3,12). Assays of NADPH-dependent hydroxypyruvate reduction in the mutant have permitted the conclusion that HPR-2 has sufficient activity to cope with the entire flux of carbon through the photosynthetic carbonoxidation (or photorespiration) pathway.…”

Section: Hpr: Recent Advancessupporting

confidence: 69%

“…The purified enzyme is sensitive to inhibition by acetohydroxamate, with a Ki of 0.3 mm (12). In contrast, HPR enzymes are not sensitive to this inhibitor (6,10). It has been demonstrated that glyoxylate reduction, with both NADPH and NADH, is acetohydroxamate sensitive in pea chloroplasts and in cytosolic supematant fractions (3) (although in the latter case the measurement of acetohydroxamate sensitivity is complicated by acetohydroxamate-dependent NAD(P)H oxidation, which must be corrected for, and which also indicates that this inhibitor must be used cautiously in complex extracts or in in vivo situations).…”

mentioning

confidence: 90%

“…Nevertheless, evidence is available that suggests that the ability of leaf extracts to reduce hydroxypyruvate need not necessarily rely exclusively on NADH as the only reductant because NADPH can also support hydroxypyruvate reduction. In view of the known ability of HPR-1 to use NADPH (albeit less efficiently than NADH) (6,14), and because of the very high activity of this enzyme, it has been thought likely that the NADPHdependent reduction of hydroxypyruvate is attributable only to HPR-1. This conclusion must now be revised.…”

Section: Hpr: Recent Advancesmentioning

confidence: 99%

“…As is discussed below, the HPR and GR enzymes have different inhibitor specificities, so that it should be possible to refine and extend the present conclusions on subcellular distribution of GR. In pea leaves, the acetohydroxamate sensitivity of both cytosolic and choroplastic glyoxylate reduction (3) indicates that the activity is largely mediated by GR, but in some monocots there is evidence for extensive participation of an HPR enzyme in reducing glyoxylate (6,8).…”

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confidence: 99%

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The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants

Givan

Kleczkowski²

1992

Plant Physiol.

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Glyoxylate and hydroxypyruvate are metabolites involved in the pathway of carbon in photorespiration. The chief glyoxylate-reducing enzyme in leaves is now known to be a cytosolic glyoxylate reductase that uses NADPH as the preferred cofactor but can also use NADH. Glyoxylate reductase has been isolated from spinach leaves, purified to homogeneity, and characterized kinetically and structurally. Chloroplasts contain lower levels of glyoxylate reductase activity supported by both NADPH

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Section: Hpr: Recent Advancessupporting

confidence: 69%

mentioning

confidence: 90%

Section: Hpr: Recent Advancesmentioning

confidence: 99%

mentioning

confidence: 99%

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The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants

Givan

Kleczkowski²

1992

Plant Physiol.

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“…Leaf HPR-1, HPR-2, and GR-1 have different immunological, kinetic, and physical characteristics (11,14,15). HPR-1 is compartmentalized exclusively in the peroxisomes (23,26,28), whereas both HPR-2 and GR-1 are found predominantly in the cytosol (6,12).…”

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confidence: 99%

Enzymology of the Reduction of Hydroxypyruvate and Glyoxylate in a Mutant of Barley Lacking Peroxisomal Hydroxypyruvate Reductase

Kleczkowski

Edwards²,

Blackwell³

et al. 1990

Plant Physiol.

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The use of LaPr 88/29 mutant of barley (Hordeum vulgare), which lacks NADH-preferring hydroxypyruvate reductase (HPR-1), allowed for an unequivocal demonstration of at least two related NADPH-preferring reductases in this species: HPR-2, reactive with both hydroxypyruvate and glyoxylate, and the glyoxylate specific reductase (GR-1). Antibodies against spinach HPR-1 recognized barley HPR-1 and partially reacted with barley HPR-2, but not GR-1, as demonstrated by Western immunoblotting and immunoprecipitation of proteins from crude leaf extracts. The mutant was deficient in HPR-1 protein. In partially purified preparations, the activities of HPR-1, HPR-2, and GR-1 could be differentiated by substrate kinetics and/or inhibition studies. Apparent Km values of HPR-2 for hydroxypyruvate and glyoxylate were 0.7 and 1.1 millimolar, respectively, while the Km of GR-1 for glyoxylate was 0.07 millimolar. The Km values of HPR-1, measured in wild type, for hydroxypyruvate and glyoxylate were 0.12 and 20 millimolar, respectively. Tartronate and P-hydroxypyruvate acted as selective uncompetitive inhibitors of HPR-2 (Ki values of 0.3 and 0.4 millimolar, respectively), while acetohydroxamate selectively inhibited GR-1 activity. Nonspecific contributions of HPR-1 reactions in assays of HPR-2 and GR-1 activities were quantified by a direct comparison of rates in preparations from wild-type and LaPr 88/29 plants. The data are evaluated with respect to previous reports on plant HPR and GR activities and with respect to optimal assay procedures for individual HPR-1, HPR-2, and GR-1 rates in leaf preparations.In photosynthetic tissues, metabolism of hydroxypyruvate and glyoxylate is thought to be intimately associated with the operation of the glycolate pathway (the oxidative photosynthetic carbon cycle), which results in photorespiration (5, 9). The pathway, which starts with P-glycolate formation by ribulose-1,5-bisP oxygenase, involves several cell compartments and is the main route for metabolism of two-carbon and some three-carbon compounds during photosynthesis (9).

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Glycerate Dehydrogenas

Rumsby¹,

Cregeen²

2002

Wiley Encyclopedia of Molecular Medicine

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Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Cited by 25 publications

References 36 publications

The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants

The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants

Enzymology of the Reduction of Hydroxypyruvate and Glyoxylate in a Mutant of Barley Lacking Peroxisomal Hydroxypyruvate Reductase

Glycerate Dehydrogenas

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