Ornithine-delta-aminotransferase catalyzes the conversion of ornithine to glutamate-gamma-semialdehyde. In humans, deficiency of this mitochondrial matrix enzyme results in the progressive blinding disorder, gyrate atrophy of the choroid and retina. To explore yeast as an expression system, we introduced a cDNA encoding human ornithine-delta-aminotransferase into an ornithine aminotransferase-deficient strain of Saccharomyces cerevisiae. The human enzyme was expressed at high levels, with activity 20-fold greater than that of wild-type yeast and 10-fold higher than in human fibroblasts. Although the normal location of ornithine-delta-aminotransferase in S. cerevisiae is cytosolic, human ornithine-delta-aminotransferase expressed in S. cerevisiae was localized to the mitochondrial matrix with correct proteolytic processing of its mitochondrial leader sequence. Despite this anomalous location in yeast, human ornithine-delta-aminotransferase complemented the phenotype of the mutant strain, restoring its ability to utilize ornithine as a sole nitrogen source. We also expressed a vitamin B6-responsive missense allele of ornithine-delta-aminotransferase (V332M) and showed that the biochemical phenotype of this allele is easily demonstrated confirming the usefulness of this system for examining mutations causing gyrate atrophy.

• PMID: 8281144
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• PubMed

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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, Non-P.H.S. | Research Support, U.S. Gov't, P.H.S.

Authors

Dougherty KM, Swanson DA, Brody LC, Valle D

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