Consequences of missense mutations for dimerization and turnover of alanine:glyoxylate aminotransferase: study of a spectrum of mutations.

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Coulter-Mackie MB, Lian Q

Consequences of missense mutations for dimerization and turnover of alanine:glyoxylate aminotransferase: study of a spectrum of mutations.

Mol Genet Metab. 2006 Dec;89(4):349-59. Epub 2006 Sep 12.

PubMed ID

16971151 [ View in PubMed

]

Abstract

Alanine:glyoxylate aminotransferase (AGT) is a liver peroxisomal enzyme, deficiency of which results in primary hyperoxaluria type 1 (PH1). More than 65 PH1-related mutations are now documented in the AGT gene (AGXT), of which about 50% are missense. We have generated a spectrum of 15 missense changes including the most common PH1 mutation, G170R, and expressed them on the appropriate background of the major or minor allele, in an Escherichia coli overexpression system and in a rabbit reticulocyte transcription/translation system. We have investigated their effects on enzyme activity, dimerization, aggregation, and turnover. The effect of pyridoxal phosphate (PLP) on dimerization and stability was also investigated. Although all 15 mutant AGTs were expressed as intact proteins in E. coli, only three: G41R and G41V on the major allele, and the common mutation G170R, resulted in significant amounts of enzymatic activity. Dimerization failure was a frequent observation (13/15) except for G41V and D183N. Dimerization was poor with S187F but was substantially improved with PLP. Proteasome-mediated protein degradation was observed for all the mutations except G41R on the major allele, G41V, D183N, G170R, and S218L. Increases in the stability of the mutant enzymes in the presence of PLP were small; however, G41R on the minor allele showed a direct relationship between its half life and the concentration of PLP. The minor allele AGT product and many of the mutants were subject to a limited non-proteasomal proteolytic cleavage when ATP was depleted.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Pyridoxal phosphate	Serine--pyruvate aminotransferase	Protein	Humans	Unknown	Cofactor	Details

Polypeptides

Name	UniProt ID
Serine--pyruvate aminotransferase	P21549	Details