Differential activity and secretion of multiple proteinases in vegetative amoebae and in germinating spores of the cellular slime mold Dictyostelium discoideum.

Lysosomal enzymes in the cellular slime mold Dictyostelium discoideum are differentially secreted during growth and starvation. Axenic amoebae linearly secreted over 30% of the total acid phosphatase activity during starvation in phosphate buffer. Addition of sucrose stimulated secretion of acid phosphatase; over 70% of the total enzyme activity was rapidly released. Moreover, the secretion kinetics of the enzyme activity shifted to a sigmoidal pattern resembling the complex secretion kinetics of other lysosomal enzymes. In an extension of these findings proteinase secretion was examined during starvation using three peptide-nitroanilide substrates N-benzoyl-L-prolyl-L-phenylalanyl-L-arginine 4-nitroanilide (BzPFR), N-carbobenzoxy-L-arginyl-L-arginine 4-nitroanilide (ZRR), and N-carbobenzoxy-L-tyrosyl-L-lysyl-L-arginine 4-nitroanilide (ZYKR). Proteinase activity was also examined in spores and during spore germination under various activation treatments. Dormant spores contained a major 58 kDa aspartic proteinase, designated ddAP58. Matrix material contained a novel 18 kDa cysteine proteinase, named ddCP18. During spore germination a decrease in intracellular ddAP58 activity heralded the appearance of two new cysteine proteinase activities, designated ddCP43 and ddCP48. Increases in BzPFRase and ZYKRase activities were also observed during emergence of myxamoebae. The use of different spore activation treatments, which altered the timing of events during germination, revealed that ZYKRase activity could be uncoupled from emergence. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1991 .F735. Source: Masters Abstracts International, Volume: 31-01, page: 0210. Thesis (M.Sc.)--University of Windsor (Canada), 1991