Development of multipurpose peroxisomes in Candida boidinii grown in oleic acid-methanol limited continuous cultures

Abstract

We have studied the development and metabolic significance of peroxisomes in the yeast Candida boidinii following adaptation of the organism to cultivation conditions which require the simultaneous presence and activity of two independent peroxisome-mediated pathways for growth. After the addition of methanol to oleic acid-grown cells at late exponentional growth, a number of new small peroxisomes developed which, apart from the presence of 1-oxidation enzymes, were characterized by the presence of enzymes involved in methanol metabolism (alcohol oxidase and dihydroxyacetone synthase). The latter proteins, however, were absent in the larger organelles which were originally present in the oleic acid-grown cells prior to the addition of methanol and which contained only enzymes of the 13-oxidation pathway. Subsequent experiments on cells from continuous cultures grown on a mixture of oleic acid and methanol at steady-state conditions revealed that both the enzymes of the 13-oxidation pathway and those involved in methanol metabolism were found in one and the same compartment. Thus, under these conditions the cells contained peroxisomes which were concurrently involved in the metabolism of two different carbon sources simultaneously used for growth. Our results indicated that the heterogeneity in the peroxisomal population of a single cell, observed in the transient state following the addition of methanol, is only temporary and due to heterogeneity among these organelles with respect to their capacity to incorporate newly synthesized matrix proteins.In yeasts, microbodies (peroxisomes and glyoxysomes) play an essential role in the metabolism of different carbon and/or organic nitrogen sources (21,22). Initially, it was thought that the organelles were of minor metabolic significance and contained only one or more catalytic functions. The finding, however, that microbodies present in methylotrophic yeasts contain not only alcohol oxidase, the key enzyme of methanol metabolism, but also dihydroxyacetone synthase (4, 7), a key enzyme in carbon assimilation under these conditions (18), together with other biosynthetic enzymes (28) stresses the importance of these organelles and clearly places their metabolic significance beyond that of a compartment purely involved in catabolism.Yeast microbodies do not arise de novo but develop by growth and fission of existing organelles (22, 23); however, experiments performed with the methylotrophic yeast Hansenula polymorpha indicated that the capacity of individual organelles to incorporate newly synthesized matrix proteins may be related to their developmental stage (24).The recent finding that, in the methylotrophic yeast Candida boidinii, massive microbody proliferation may be induced by carbon sources other than methanol (9, 16) makes it possible to study the development and functioning of the microbodies during the growth of cells in media supplemented with more than one carbon source, each of which is metabolized via specific peroxisome-mediated metabolic pathways. The pre...

Environmentally Regulated Glycosome Protein Composition in the African Trypanosome

“…After reaching a threshold size, the organelles give rise to new ones through fission. The progenitor organelle is metabolically active but no longer capable of importing new protein (32,33). To our knowledge, the presence of a de novo biogenesis process or sequential glycosome maturation in T. brucei has never been examined, and to date, database analysis has failed to reveal a PEX3 homolog.…”

The Peroxin Pex17p of the Yeast Yarrowia lipolytica Is Associated Peripherally with the Peroxisomal Membrane and Is Required for the Import of a Subset of Matrix Proteins

“…Wild-type Y. lipolytica E122 cells were chemically mutagenized with 1-methyl-3-nitro-1-nitrosoguanidine, and the pex17-1 strain was initially isolated by its inability to utilize oleic acid as the carbon source (26). Further screening of the pex17-1 strain included analysis by electron microscopy (25,35) and subcellular fractionation (1). Mutant strains were characterized by standard genetic techniques for Y. lipolytica (14).…”

The N‐terminus of amine oxidase of Hansenula polymorpha contains a peroxisomal targeting signal

“…Crude extracts were prepared as described [17]. Protein concentrations were determined with the Bio-Rad protein assay kit using bovine serum albumin as a standard.…”