Yeast peroxisomes: structure, functions and biotechnological opportunities

Abstract

Peroxisomes are ubiquitous organelles found in most eukaryotic cells. In yeasts, peroxisomes play important roles in cell metabolism, especially in different catabolic processes including fatty acid β-oxidation, the glyoxylic shunt and methanol metabolism, as well as some biosynthetic processes. In addition, peroxisomes are the compartment in which oxidases and catalase are localized. New peroxisomes mainly arise by fission of pre-existing ones, although they can also be formed from the endoplasmic reticulum (ER). Peroxisomes consist of matrix-soluble proteins and membrane proteins known as peroxins. A total of 34 PEX peroxin genes and proteins have been identified to date. and their functions have been elucidated. Protein import into peroxisomes depends on peroxins and requires specific signals in the structure of transported proteins: PTS1, PTS2 and mPTS. The mechanisms of metabolite penetration into peroxisomes are still poorly understood. Peroxisome number and the volume occupied by these organelles are tightly regulated. Methanol, fatty acids and methylamine act as efficient peroxisome proliferators, whereas glucose and ethanol induce peroxisome autophagic degradation (pexophagy). To date, 42 Atg proteins involved in pexophagy are known. Catabolism and alcoholic fermentation of the major pentose sugar, xylose, depend on peroxisomal enzymes. Overexpression of peroxisomal transketolase and transaldolase activates xylose fermentation. Peroxisomes could be useful as target organelles for overexpression of foreign toxic proteins.

Analysis of autophagy activated during changes in carbon source availability in yeast cells

“…Rather, both organelles increased during the ethanol-utilizing phase. Because lipases for triacylglycerols and steryl esters are localized in LDs (37)(38)(39)(40), fatty acids may be produced via lipolysis in the cytosol, converted to acyl-CoA, and assimilated in the peroxisome, which has ␤-oxidation activity in yeast, in the ethanol-depleted phase (41). The mitochondria should be needed to produce ATP, but the required amount of the mitochondria may be less in the ethanol-depleted phase than the ethanol-utilizing phase.…”

Pexophagy: A Model for Selective Autophagy

“…It is not known whether fission is similarly required for mammalian pexophagy. However, as peroxisomes in mammalian cells are significantly smaller than in methylotrophic yeasts [155] it is possible that fission is not a requisite for peroxisome sequestration within autophagosomes.…”

Temporal profiling of redox-dependent heterogeneity in single cells

“…2A, F). As a control we deleted Pex3, an essential peroxisomal protein 26 , leading to a complete loss of peroxisomes and the distribution of the peroxisomal sensor back to the cytosol ( Fig. 2B, F).…”