Structural basis of substrate specificity in human glyoxylate reductase/hydroxypyruvate reductase.

Abstract	Human glyoxylate reductase/hydroxypyruvate reductase (GRHPR) is a D-2-hydroxy-acid dehydrogenase that plays a critical role in the removal of the metabolic by-product glyoxylate from within the liver. Deficiency of this enzyme is the underlying cause of primary hyperoxaluria type 2 (PH2) and leads to increased urinary oxalate levels, formation of kidney stones and renal failure. Here we describe the crystal structure of human GRHPR at 2.2 A resolution. There are four copies of GRHPR in the crystallographic asymmetric unit: in each homodimer, one subunit forms a ternary (enzyme+NADPH+reduced substrate) complex, and the other a binary (enzyme+NADPH) form. The spatial arrangement of the two enzyme domains is the same in binary and ternary forms. This first crystal structure of a true ternary complex of an enzyme from this family demonstrates the relationship of substrate and catalytic residues within the active site, confirming earlier proposals of the mode of substrate binding, stereospecificity and likely catalytic mechanism for these enzymes. GRHPR has an unusual substrate specificity, preferring glyoxylate and hydroxypyruvate, but not pyruvate. A tryptophan residue (Trp141) from the neighbouring subunit of the dimer is projected into the active site region and appears to contribute to the selectivity for hydroxypyruvate. This first crystal structure of a human GRHPR enzyme also explains the deleterious effects of naturally occurring missense mutations of this enzyme that lead to PH2.
Authors	Michael P S Booth, R Conners, Gill Rumsby, R Leo Brady
Journal	Journal of molecular biology (J Mol Biol) Vol. 360 Issue 1 Pg. 178-89 (Jun 30 2006) ISSN: 0022-2836 [Print] Netherlands
PMID	16756993 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Alcohol Oxidoreductases glyoxylate reductase Hydroxypyruvate Reductase
Topics	Alcohol Oxidoreductases (chemistry) Crystallography, X-Ray Dimerization Humans Hydroxypyruvate Reductase (chemistry) Kinetics Models, Chemical Molecular Conformation Mutation Protein Binding Protein Conformation Substrate Specificity

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