Regulation of Enzyme Activity During Differentiation in Dictyostelium Discoideum

The Inactivation of Microbial Enzymes in Vivo

“…Many casual reports of the loss of enzyme activity from microbial cells exist, but I have attempted to concentrate on those cases in which the inactivation process itself was a focus of attention. Cases of the inactivation of enzymes in phage-infected bacteria (29,47,81,99,109,131) and in differentiating slime molds (2,43,64,125) have not been included because of space limitations and because of their specialized nature. Table 1 lists 41 examples of reasonably well-characterized inactivation processes occurring in microbes that were found in a survey of the literature from about 1945 to mid 1976.…”

“…Protein degradation and inactivation of specific proteins during ascospore formation in yeast have been described by Betz & Weiser (Sa). Examples from differentiating slime molds have been reviewed elsewhere (2,43,64,125). In the instances cited the differentiation is generally elicited by a change in the carbon or nitrogen metabolism, however, and the involvement of enzyme inactivation in an event specifically concerned with microbial morphogenesis has not been proven.…”

“…Some methods of detecting and avoiding such artifacts were presented. (iii) Because the intracellular concentration of some enzymes appears to be regulated by excretion in the differentiating slime molds (43,64,91), one must determine whether an enzyme that disappears from microbial cells can be found in the growth medium and, when fi ndings are negative, demonstrate that the enzyme in question could have been detected at the expected levels in the culture medium by the assay used. At least one instance of inactivation of an extracellular enzyme by an extracellular protein, possibly a proteinase, is known (28).…”

“…(iv) Inactivation of an enzyme can be mimicked by transfer of the enzyme to a subcellular compartment that is impermea ble to assay reagents or discarded during preparation of extracts. A fraction of the soluble glycogen synt�etase of Dictyostelium discoideum undergoes such an associa tion with insoluble cell wall material during culmination (43,64). Therefore it is necessary to examine unfractionated extracts, cell debris, and extracts prepared by a variety of rupture methods to ensure detection of any enzyme rendered cryptic by transfer to a subcellular compartment.…”

Protein synthesis during development and differentiation in the cellular slime mould Dictyostelium discoideum

“…The only other cell-type-specific enzyme se (Firtel that has been identified is an isoenzyme of acid phosphatase of unknown function which is restricted to pre-stalk cells (Armant & Rutherford, 1979;Oohata, 1983 Loomis, 1969cLoomis, , 1975. By contrast, Wright and her colleagues obtained results which indicated that the increases in specific activity of many of the developmentally regulated enzymes were not dependent on increased synthesis of the enzyme proteins (see Gustafson & Wright, 1972;Killick & Wright, 1974) and it was suggested that actinomycin D and cycloheximide might not be having their effects on enzyme specific activity by inhibiting protein synthesis (Wright, 1972, but see also Sussman, 1972). Instead it seemed that the enzymes were at constant concentration in cells throughout development and that increases in enzyme specific activity could be detected for the following reasons.…”