Phosphodiesterase I and

In another approach subcellular fractionation of human PMNs, stimulated in vitro with phorbol myristate acetate or opsonized zymsan, was performed by rate-zonal centrifugation in sucrose gradients By varying the centrifugal force the NADPH oxidase could be separated from the activities of enzymes in the lysosomal granules but was similar to the distribution of markers for the plasma membrane, aryl phosphatase, alkaline phosphodiesterase I, and acid aryl phosphatase. 

RNA degradation up to 50°C gives a preferential activity of phosphodiesterase I, and leads to the liberation of 5 -nucleotides. An increased activity of enzymes, liberating 2,3 -nucleot des, can be found only at higher temperatures and a later stage, when the substrate has already been used up by phosphodiesterase I. 

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