THE METABOLISM OF VALERATE-3-C14 AND -5-C14 BY WHEAT STEM RUST UREDOSPORES

Abstract

Uredospores of wheat stem rust took up about 90% of the carbon-14 present either as valerate-3-C14 or as valerate-5-C14 in M/30 phosphate buffer pH 6.2 in 3 hours. The initial valerate concentration was 0.017 mM and spores were supplied at the rate of 250 mg/30 ml of buffer. Carbon 3 of the valerate was largely respired as carbon dioxide but carbon 5 was extensively incorporated into spore components. Free amino acids contained about 40% of the radioactivity in the spores labelled with valerate-5-C14 and glutamic acid was highly labelled. Carbon 1 contained 8.1% and carbon 5, 3.8% of the carbon-14 in this glutamic acid and thus internal carbons contained 88%. The results with valerate-3-C14 and with valerate-5-C14 compare well with those of experiments done earlier with propionate-1-C14 and propionate-3-C14 respectively. It is concluded that propionate is formed from carbons 3, 4, and 5 of valerate, and thus that carbon 3 is converted to carbon dioxide, and carbons 4 and 5 to the carboxyl and methyl groups respectively of acetate.