Cysteine proteinase changes during microcyst formation and germination inPolysphondylium pallidum

Microcyst formation inPolysphondylium pallidum WS320 was accompanied by a decrease in intracellular cysteine proteinase activity measured with the peptide nitroanilides Z-Arg-Arg-Nan and Bz-Pro-Phe-Arg-Nan. Some activity was released into the buffer, and secretion of that towards Z-Arg-Arg-Nan continued until encystment occurred. Cells grown in association withEscherichia coli had an electrophoretic proteinase pattern different from cells grown axenically. Microcysts formed from the two cell populations also had distinct proteinase patterns; those from bacterially grown cells retained significant quantities of proteinase ppCP22, whereas those derived from axenic cells were devoid of detectable proteinases. No significant changes in cysteine proteinase activities were observed during microcyst germination, although some changes in activity occurred subsequent to emergence. The results indicate that there is not a close correlation between particular cysteine proteinases and specific stages of microcyst formation. Intracellular proteinase loss and concomitant secretion are, however, processes typical of cellular slime molds developing in response to starvation.