title: Developmentally regulated enzymes and cyclic AMP-binding sites in Dictyostelium discoideum cells blocked during development by alpha-chymotrypsin.
abstract: When cells of the slime mould Dictyostelium discoideum are allowed to starve in the presence of alpha-chymotrypsin, they are blocked in development at the stage where tight aggregates form tips. Analysis of developmentally regulated enzymes has shown that alpha-mannosidase, beta-N-acetylglucosaminidase, threonine deaminase, tyrosine aminotransferase, beta-glucosidase and the carbohydrate-binding protein discoidin are unaffected, but enzymes that show an increase in specific activity during post-aggregative development, namely glycogen phosphorylase, UDP-glucose pyrophosphorylase, UDP-galactose 4-epimerase, UDP-galactose polysaccharide transferase and alkaline phosphatase, did not show the characteristic increase when development was blocked by alpha-chymotrypsin. Recovery of cells from the effects of alpha-chymotrypsin was accompanied by the formation of fruiting bodies and a concomitant increase in the specific activity of UDP-glucose pyrophosphorylase. Uptake or efflux of 45Ca2+ was not altered in the presence of alpha-chymotrypsin. Cells allowed to develop in alpha-chymotrypsin, or treated with the enzyme for 15 min, had a markedly reduced ability to bind cyclic AMP with low affinity; high-affinity binding was unaffected. Pronase had a similar effect on cyclic AMP binding, but trypsin, which does not alter developmental processes, has no effect on cyclic AMP binding to D. discoideum cells.
mesh_terms: D002118:Calcium / Q000378:metabolism; D002449:Cell Aggregation / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002918:Chymotrypsin / Q000494:pharmacology*; D004023:Dictyostelium / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D011953:Receptors, Cyclic AMP / Q000187:drug effects*; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000378:metabolism
chemical_list: D011953:Receptors, Cyclic AMP; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase; D002918:Chymotrypsin; D002118:Calcium