Further studies on a unique T-tubular acid phosphatase in avian skeletal muscle

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Abstract
Summary Whith the unique observation, using conventional cytochemistry, of acid phosphatase reaction production in the T-tubules of the posterior latissimus dorsi muscle of the chicken, the possibility of andocytosis of lysosomal enzymes by muscle cells came into question. After testing the substrate specificity of this T-tubular phosphatase, it was clear that the enzyme was not 5′-nucleotidase for a typical lysosomal acid phosphatase. The T-tubular enzyme hydrolysed glucose 6-phosphate and β-glycerophosphate at pH 5.0 but not cytidine-5′-monophosphate which was hydrolysed by dense bodies and autophagic vacuoles. The cytochemical evidence points to a mique phosphatase present on mucle cell membranes which apparently does not belong to the vacuolar apparatus of skeletal muscle and is not 5′-nucleotidase.