Differential compartmentation of ornithine decarboxylase in cells of Mucor vouxii

Summary: A study was made to obtain an explanation for the differential effect in Mucorales of the ornithine decarboxylase (ODC) inhibitors 1,4-diamino-2-butanone (DAB) and α-difluoromethylornithine (DFMO), only the first of which affects cell differentiation; and for the paradoxical result that while it inhibits this process, DAB has no further effect on cell growth. Results obtained with cells permeabilized by two different methods which respectively do or do not affect internal membranes, and with protoplasts lysed under iso-osmotic conditions, suggest that the plasmalemma from M. rouxii cells is permeable to DAB, but not to DFMO, and that ODC is present in more than one cell compartment. ODC from the distinct cell compartments was differentially accessible to its substrate, and to DAB or DFMO, providing a reasonable explanation for the above results.