Regulation of polyamine synthesis in physarum polycephalum during growth and differentiation

Synthesis of protein during the nuclear division cycle in Physarum polycephalum

“…Determination of the accumulation curve for total protein by direct application of the isotope-dilution method, prelabelling the inoculum with a radioactive amino acid and then measuring the decrease in the specific activity of plasmodial protein, would not be acceptable because many proteins probably have halflives that are significantly short in relation to the growth rate of a plasmodium [3]. However, the isotope-dilution method can be applied indirectly by prelabelling the metabolically stable nucleic acids and then, in samples from a surface plasmodium, determining both the specific activity of the nucleic acid (S) and the amounts of nucleic acid (iV) and protein (P).…”

Cycloheximide induced in vivo modification of ornithine decarboxylase in Physarum polycephalum

“…Since the control of polyamine levels has been shown to be important in cystic fibrosis [8], cancerous growth [6,9,11], and chemotherapy [ 12,131, it is essential that the mode of regulation of this important enzyme be clarified. Here we lzport that the rapid decay in the ornithine decarboxylase activity of Physarum polycephalum [3] is associated with a reversible modification of the enzyme. Within 100 min of the inhibition of protein synthesis by cycloheximidc, the apparent Km of the pyridoxal-5'-phosphate (PLP) activation of this enzyme varied seven-fold, while the Km for the substrate, ornithine, was unchanged.…”

“…Enzyme activity was determined by measuring the liberation of ' 4 CO2 from DL-[ 1 -I4 C] ornithine as detailed earlier [3], except hyamine hydroxide was used to absorb the 14C02 which was counted in a toluene-based scintillation fluid. The incubation mixtures are described in the figure legends.…”

“…Since there is no detectible ornithine decarboxylase activity in crude enzyme preparations without added PLP [3], we also tested the ability of this coenzyme to stimulate activity as a possible indication of an altered enzyme state. Each of the nine enzyme fractions from the experiment illustrated in fig.…”

S-adenosylmethionine decarboxylase from baker's yeast

“…The classification of adenosylmethionine decarboxylases into putrescine-activated eukaryotic enzymes and Mg2+-dependent prokaryotic enzymes, however, has a number of important exceptions. Thus adenosylmethionine decarboxylase from bean sprouts (Coppoc etal., 1971), from the slime mould Physarum polycephalum (Mitchell & Rusch, 1973) and from the protozoan Tetrahymena pyriformis (Poso et al, 1975) is not stimulated by putrescine. In contrast with the plant enzyme, which requires Mg2+ (Coppoc et al, 1971), the plasmodium enzyme (Mitchell & Rusch, 1973) and the protozoan enzyme (Poso et al, 1975) do not need any metal ion.…”