Inducible beta-oxidation pathway in Neurospora crassa.

An inducible beta-oxidation system was demonstrated in a particulate fraction from Neurospora crassa. The activities of all individual beta-oxidation enzymes were enhanced in cells after a shift from a sucrose to an acetate medium. The induction was even more pronounced in transfer to a medium containing oleate as sole carbon and energy source. Since an acyl-coenzyme A (CoA) dehydrogenase was detected instead of acyl-CoA oxidase, the former enzyme seems to catalyze the first step of the beta-oxidation sequence in N. crassa. After isopycnic centrifugation in a linear sucrose gradient, the intracellular organelles housing the fatty acid degradation pathway cosedimented (1.21 g/cm3) with the glyoxylate bypass enzymes isocitrate lyase and malate synthase and were clearly resolved from both mitochondrial marker enzymes (1.19 g/cm3) and catalase (1.26 g/cm3). On the basis of biochemical as well as morphological properties, these particles from N. crassa have recently been designated as glyoxysome-like particles (G. Wanner and T. Theimer, Ann. N.Y. Acad. Sci. 386:269-284, 1982). The failure to detect catalase, urate oxidase, and acyl-CoA oxidase indicate that these glyoxysome-like microbodies in N. crassa lack peroxisomal function and thus are clearly different from the various microbodies reported so far to contain a beta-oxidation pathway.