Enzymic Conversion of Mononucleotides by Rat Diaphragm in vitro.

Summary. The enzymatic conversion of mononucleotides by the isolated rat diaphragm during incubation in Krebs Ringer phosphate medium has been investigated. This has been achieved by adding several different mononucleotides to the incubation medium and fractionation of the reaction products by a chromatographic procedure on an anion exchange resin. Dephosphorylating as well as transphosphorylating enzymic activity are exerted by the rat diaphragm in vitro . Particularly the presence of ATPase, myokinase, 5'adenylic acid deaminase and nucleoside diphosphokinase has been demonstrated. The breakdown of ATP added to the medium proceeds by the sequence ATP + ADP – AMP –. IMP –f Inosine. By addition of ITP, GTP, CTP, and UTP, these nucleoside triphosphates are broken down to the corresponding diphosphate and mono‐phosphate derivatives. Indications have been obtained that ATPase is firmly bound at or near the muscle cell surface. On the other hand a leakage of myokinase, 5′ adenylic acid deaminase and nucleoside diphospho‐kinase from the diaphragm into the medium during incubation has been demonstrated.