THE BREAKDOWN OF ADENOSINE PHOSPHATES IN EXTRACTS OF XANTHOMONAS PHASEOLI

Abstract

Cell-free extracts of Xanthomonas phaseoli (XP8) can convert ATP to hypoxanthine, the chief intermediates being ADP, AMP, IMP, and inosine. The following enzymes concerned in the breakdown of ATP are present: adenosine triphosphatase, myokinase, adenylic acid deaminase, a 5′-nucleotidase acting on IMP, and a nucleosidase which converts inosine to hypoxanthine. It is concluded that the conversion of ADP to AMP is, for the most part, carried out by the myokinase, the direct dephosphorylation of ADP being of questionable significance in these extracts.AMP is not dephosphorylated directly but is first deaminated to IMP. A method is presented which allows enzymatic deamination to be studied by manometric means. The deamination of AMP is found to explain the biphasic nature of the carbon dioxide output and uptake observed when hexokinase activity of extracts is measured by the manometric method.