Abstract
A specific pterin deaminase has been detected in rat liver. The enzyme was purified 23-fold. During its purification, guanine deaminase (EC 3.5.4.3) activity of the protein was increased 39-fold. Evidence is given which establishes the nonidentity of pterin deaminase and guanine deaminase: changes in the ratio of their activities during preparation; differences in stability during storage and inhibition by CN − and by azaguanine and guanine; differences in the pH maxima and in the distribution of enzyme activities in various organisms. The reaction maximum is at pH 6.5 and K m is 30 μM. The enzyme specifically deaminates pterin, isoxanthopterin and tetrahydropterin. Xanthopterin, biopterin, neopterin, pterin-6-carboxylic acid, and 6-hydroxymethylpterin are not deaminated. In the honeybee ( Apis mellifica), pterin deaminase activity has also been detected. The highest activity has been found in 4-day-old larvae.
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