the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
enzyme HPR2 shows relaxed substrate and cofactor specificity, it also has glyoxylate reductase (NADP+) activity (EC 1.1.1.79). Irreversibility of the HPR2 reaction has been reported
enzyme HPR2 shows relaxed substrate and cofactor specificity, it also has glyoxylate reductase (NADP+) activity (EC 1.1.1.79). Irreversibility of the HPR2 reaction has been reported
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
the recombinant AtHPR1 prefers NADH over NADPH and hydroxypyruvate over glyoxylate. Isozyme AtHPR1 also converts glyoxylate to glycolate, albeit with much lower catalytic efficiency than for hydroxypyruvate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
HPR3 prefers NADPH over NADH and converts glycerate to hydroxypyruvate, the purified recombinant HPR3 shows similar activity with hydroxypyruvate and glyoxylate
the enzyme belongs to the beta-HAD (beta-hydroxyacid dehydrogenase) protein family. AtHPR2 and AtHPR3 are 45% identical to each other at the amino acid level, but only 19-25% identical to AtHPR1, the NADH-dependent form, and 8-9% identical to the AtGLYRs. None of the AtHPRs contains the active-site residues conserved in AtGLYR1 and AtGLYR2, indicating that the sites responsible for reducing glyoxylate differ greatly between the AtGLYRs and AtHPRs
in vitro characterization of the recombinant proteins reveals that HPPR2 has both hydroxypyruvate reductase (HPR EC 1.1.1.81, main activity) and hydroxyphenylpyruvate reductase (HPPR, EC 1.1.1.237) activities, whereas HPPR3 has a strong preference for pHPP, and both enzymes are localized in the cytosol. In Arabidopsis thaliana, HPPR2 and HPPR3, together with tyrosine aminotransferase 1 (TAT1), constitute to a probably conserved biosynthetic pathway from tyrosine to 4-hydroxyphenyllactic acid (pHPL), from which some specialized metabolites, such as rosmarinic acid (RA), can be generated in specific groups of plants. Role of HPPR in the tyrosine conversion pathway, overview
the enzyme belongs to the beta-HAD (beta-hydroxyacid dehydrogenase) protein family. AtHPR2 and AtHPR3 are 45% identical to each other at the amino acid level, but only 19-25% identical to AtHPR1, the NADH-dependent form, and 8-9% identical to the AtGLYRs. None of the AtHPRs contains the active-site residues conserved in AtGLYR1 and AtGLYR2, indicating that the sites responsible for reducing glyoxylate differ greatly between the AtGLYRs and AtHPRs
no hydroxyphenylpyruvate reductase (HPPR) activity by isozyme HPPR4 from Arabidopsis thaliana. Isozyme HPPR2 mainly shows hydroxypyruvate reductase (HPR) activity, while isozyme HPPR3 mainly shows 4-hydroxyphenylpyruvate reductase (EC 1.1.1.237) activity. Enzyme HPPR2 belongs to the family of D-isomer-specific 2-hydroxyacid dehydrogenases, group II
Arabidopsis thaliana mutants defective in either HPPR2 or HPPR3 isozyme contain lower amounts of pHPL and are impaired in conversion of tyrosine to pHPL. Furthermore, a loss-of-function mutation in tyrosine aminotransferase (TAT) also reduces the pHPL accumulation in plants
deletion of HPR2 results in elevated levels of hydroxypyruvate and other metabolites in leaves. Photosynthetic gas exchange is slightly altered, especially under long-day conditions. Otherwise, the mutant closely resembles wild-type plants. The combined deletion of both HPR1 and HPR2 results in distinct air-sensitivity and a dramatic reduction in photosynthetic performance. Knockout of both HPR1 and HPR2 alters steady-state metabolite profiles. Knockout of either HPR1 or HPR2 alters photosynthetic gas exchange
deletion of HPR3 results in slightly altered leaf concentrations of the photorespiratory intermediates HP, glycerate, and glycine, indicating a disrupted photorespiratory flux, but not in visible alteration of the phenotype. The combined deletion of HPR1, HPR2, and HPR3 causes increased growth retardation, decreased photochemical efficiency, and reduced oxygen-dependent gas exchange in comparison with the hpr1xhpr2 double mutant. HPR mutants show impaired growth and contain less chlorophyll, phenotypes, detailed overview
deletion of photorespiratory enzymes typically leads to a strong air sensitivity of the respective mutants, which can be fully recovered by elevated-CO2 conditions. While this is a distinctive feature of most photorespiratory mutants, Arabidopsis thaliana HPR1 knockout mutants grow nearly normally in ambient air with moderate photoperiods and show only minor changes in photosynthetic and metabolic parameters under these conditions. The additional deletion of the cytosolic HPR2 distinctly elevates the oxygen sensitivity, but this hpr1xhpr2 double mutant can still survive long-term exposure to ambient air
deletion of any of the core enzymes of the photorespiratory cycle, one of the major pathways of plant primary metabolism, results in severe air-sensitivity of the respective mutants with the exception of the peroxisomal enzyme hydroxypyruvate reductase, HPR1, due to the existence of a second hydroxypyruvate reductase, HPR2, in the cytosol, overview. The enzyme provides a cytosolic bypass to the photorespiratory core cycle in Arabidopsis thaliana
deletion of isoform HPR3 results in slightly altered leaf concentrations of the photorespiratory intermediates HP, glycerate, and glycine, indicating a disrupted photorespiratory flux, but not in visible alteration of the phenotype.The combined deletion of of isoforms HPR1, HPR2, and HPR3 causes increased growth retardation, decreased photochemical efficiency, and reduced oxygen-dependent gas exchange in comparison with the hpr1hpr2 double mutant. Isoform HPR3 could provide a compensatory bypass for the reduction of hydroxypyruvate and glyoxylate within the chloroplast
Arabidopsis mutants defective in either isoform HPPR2 or HPPR3 contain lower amounts of 4-hydroxyphenyllactic acid and are impaired in conversion of tyrosine to 4-hydroxyphenyllactic acid
HPR3 is the third enzyme in Arabidopsis (Arabidopsis thaliana), which also reduces 4-hydroxypyruvate (HP) to glycerate and shows even more activity with glyoxylate, a more upstream intermediate of the photorespiratory cycle. In silico analysis and proteomic studies target HPR3 to the chloroplast, the enzyme might provide a compensatory bypass for the reduction of HP and glyoxylate within this compartment
hydroxyphenylpyruvate reductase (HPPR), which catalyzes the reduction of 4-hydroxyphenylpyruvic acid (pHPP) to 4-hydroxyphenyllactic acid (pHPL), is the key enzyme in the biosynthesis of rosmarinic acid (RA) from tyrosine and, so far, HPPR activity is reported only from the RA-accumulating plants
the enzyme activity shows that photorespiratory metabolism is not confined to chloroplasts, peroxisomes, and mitochondria but also extends to the cytosol. The extent to which cytosolic reactions contribute to the operation of the photorespiratory cycle in varying natural environments might be dynamically regulated by the availability of NADH in the context of peroxisomal redox homeostasis. But isozyme HPR1 plays the dominant role in photorespiration
HPR1 knockout plants show slight visually noticeable impairments in air. Under shorter daylengths of 8 h, somewhat slower growth of the hpr1 mutants than of the wild-type, in combination with an approximately 4-week delay in bolting. Combined deletion of both HPR1 and HPR2 (EC 1.1.1.81) results in distinct air-sensitivity and a dramatic reduction in photosynthetic performance
HPR1 knockout plants show slight visually noticeable impairments in air. Under shorter daylengths of 8 h, somewhat slower growth of the hpr1 mutants than of the wild-type, in combination with an approximately 4-week delay in bolting. Combined deletion of both HPR1 and HPR2 (EC 1.1.1.81) results in distinct air-sensitivity and a dramatic reduction in photosynthetic performance
HPR1 knockout plants show slight visually noticeable impairments in air. Under shorter daylengths of 8 h, somewhat slower growth of the hpr1 mutants than of the wild-type, in combination with an approximately 4-week delay in bolting. Combined deletion of both HPR1 and HPR2 (EC 1.1.1.81) results in distinct air-sensitivity and a dramatic reduction in photosynthetic performance
construction of hpr1 knockout and hpr2 knockout. Deletion of HPR2 results in elevated levels of hydroxypyruvate and other metabolites in leaves, photosynthetic gas exchange is slightly altered, especially under long-day conditions. Deletion of HPR1 does not show a severe phenotype, overview. The combined deletion of HPR1 and HPR2 is detrimental to air-grown mutants and alters steady state metabolite profiles, phenotypes, overview. The most prominent naturally occuring mutation causes the decrease in Ala content coupled with enhanced levels of Arg, Asn, and Asp in the hpr1 mutant and the double knockout plant
construction of hpr1 knockout and hpr2 knockout. Deletion of HPR2 results in elevated levels of hydroxypyruvate and other metabolites in leaves, photosynthetic gas exchange is slightly altered, especially under long-day conditions. Deletion of HPR1 does not show a severe phenotype, overview. The combined deletion of HPR1 and HPR2 is detrimental to air-grown mutants and alters steady state metabolite profiles, phenotypes, overview. The most prominent naturally occuring mutation causes the decrease in Ala content coupled with enhanced levels of Arg, Asn, and Asp in the hpr1 mutant and the double knockout plant
construction of hpr1 knockout and hpr2 knockout. Deletion of HPR2 results in elevated levels of hydroxypyruvate and other metabolites in leaves, photosynthetic gas exchange is slightly altered, especially under long-day conditions. Deletion of HPR1 does not show a severe phenotype, overview. The combined deletion of HPR1 and HPR2 is detrimental to air-grown mutants and alters steady state metabolite profiles, phenotypes, overview. The most prominent naturally occuring mutation causes the decrease in Ala content coupled with enhanced levels of Arg, Asn, and Asp in the hpr1 mutant and the double knockout plant
deletion of HPR2 by T-DNA insertion, HPR2 knockout plants do not show visually noticeable impairments in air, but combined deletion of HPR1 and HPR2 is detrimental to air-grown mutants. Crossing of hpr1-1 and hpr2-1 leads to functional inactivation of both genes. Knockout of both HPR1 and HPR2 alters steady-state metabolite profiles and photorespiratory 13C fluxes. The leaf glycerate content remains essentially unaltered in the hpr2 mutant and is increased in hpr1 and the double knockout plant. Knockout of either HPR1 or HPR2 alters photosynthetic gas exchange
deletion of HPR2 by T-DNA insertion, HPR2 knockout plants do not show visually noticeable impairments in air, but combined deletion of HPR1 and HPR2 is detrimental to air-grown mutants. Crossing of hpr1-1 and hpr2-1 leads to functional inactivation of both genes. Knockout of both HPR1 and HPR2 alters steady-state metabolite profiles and photorespiratory 13C fluxes. The leaf glycerate content remains essentially unaltered in the hpr2 mutant and is increased in hpr1 and the double knockout plant. Knockout of either HPR1 or HPR2 alters photosynthetic gas exchange
deletion of HPR3 by T-DNA insertion mutagenesis resulting in slightly altered leaf concentrations of the photorespiratory intermediates HP, glycerate, and glycine, indicating a disrupted photorespiratory flux, but not in visible alteration of the phenotype. The combined deletion of HPR1, HPR2, and HPR3 causes increased growth retardation, decreased photochemical efficiency, and reduced oxygen-dependent gas exchange in comparison with the hpr1xhpr2 double mutant. Generation of two independent T-DNA insertion lines for the gene At1g12550, i.e. hpr3-1 and hpr3-2
deletion of HPR3 by T-DNA insertion mutagenesis resulting in slightly altered leaf concentrations of the photorespiratory intermediates HP, glycerate, and glycine, indicating a disrupted photorespiratory flux, but not in visible alteration of the phenotype. The combined deletion of HPR1, HPR2, and HPR3 causes increased growth retardation, decreased photochemical efficiency, and reduced oxygen-dependent gas exchange in comparison with the hpr1xhpr2 double mutant. Generation of two independent T-DNA insertion lines for the gene At1g12550, i.e. hpr3-1 and hpr3-2
generation of Arabidopsis thaliana HPR1 knockout mutants, which grow nearly normally in ambient air with moderate photoperiods and show only minor changes in photosynthetic and metabolic parameters under these conditions. The additional deletion of the cytosolic HPR2 distinctly elevates the oxygen sensitivity, but this hpr1xhpr2 double mutant can still survive long-term exposure to ambient air
generation of Arabidopsis thaliana HPR1 knockout mutants, which grow nearly normally in ambient air with moderate photoperiods and show only minor changes in photosynthetic and metabolic parameters under these conditions. The additional deletion of the cytosolic HPR2 distinctly elevates the oxygen sensitivity, but this hpr1xhpr2 double mutant can still survive long-term exposure to ambient air