Peroxisomes induced in Candida Boidinii by methanol, oleic acid and d-alanine vary in metabolic function but share common integral membrane proteins

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Abstract
Peroxisomes massively proliferate in the methylotrophic yeast Candida boidinii when cultured on methanol as the only carbon and energy source. These organelles contain enzymes that catalyze the initial reactions of methanol utilization. The membranes contain abundant proteins of unknown function; their apparent molecular masses are 20, 31, 32 and 47 × 10(3) Mr and are termed PMP20, PMPs31-32 and PMP47. Recently, we reported that peroxisomes in this yeast are also induced by oleic acid and D-alanine as carbon sources, and that these peroxisomes contain increased concentrations of the enzymes of fatty acid beta-oxidation or D-amino acid oxidase, respectively. This report extends these findings and further compares the enzyme composition from peroxisomes induced by methanol, oleic acid and D-alanine. the patterns of matrix proteins represented on SDS-polyacrylamide gels from peroxisomes induced by oleic acid or D-alanine were found to be very different from those of peroxisomes induced by methanol. In order to differentiate between membrane proteins that have specific functions in pathways of substrate utilization from those with more generalized functions, peroxisomal membranes from cultures grown on methanol, oleic acid or D-alanine were purified. Analysis of these fractions demonstrated that while PMP20 is found only in peroxisomes induced by methanol, the PMPs31-32 and PMP47 were the abundant peroxisomal membrane proteins (PMP) regardless of inducing substrate. The data strongly suggest that the function of PMP20 is related to methanol metabolism. In contrast, the functions of PMPs31-32 and PMP47 are ‘substrate-nonspecific’. We speculate that they may relate to the structure, assembly or general function of the organelle.