Cereal phosphatases

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Abstract
Two rapid methods are described for the assay of free phospho-monoesterase activity in cereals in terms of already established units. The optimal pH for this activity in wheat is 515; activity disappears between pH 4 and 3, and between 6 and 7. Thermal destruction of wheat phosphomonoes-terase is appreciable at 45[degree]C and very rapid at 60[degree]C; the critical inactivation temperature in acetate buffer is 53[degree] and thermal inactivation is irreversible. Wheat phospho-monoesterase was not activated by Mg++ (10-6 to 10-4 [image]) nor by HCN (10-2.7 to 10-5 [image]); nor was it inhibited by iodoacetic acid (10-2 to 10-6 [image]). NaF was strongly inhibitory in a non-competitive manner. There are probably 2 phosphomonoesterases in wheat, of which at least one hydrolyses [alpha] glycerophosphate more rapidly than [beta] glycerophosphate. The total free phosphomonoesterase activity of wheat is greater in respect of [alpha]- than [alpha] glycerophosphate. Wheat also contains free hexosediphosphatase, pyrophos-phatase and phospho-diesterase.