Adenosine-2 ,5-diphosphate deamination

AMP aminohydrolase, an enzyme relatively specific for AMP, has been observed in reptiles (44), erythrocytes (38), snail (45), unfertilized fish eggs (46), invertebrates (47), a variety of mammalian tissues (20), and a particulate fraction of pea seeds (48). Evidence suggests that the frog muscle AMP aminohydrolase is located within or just beneath the sarcolemma (49). The rabbit skeletal and heart muscle enzymes were found in the cytoplasm and mitochondria (20, Jfi, 50, 51), while the enzyme of kidneys and gills of freshwater fish was located in the cytoplasmic fraction (52). The enzyme occurs in most areas of the rat (53) and rabbit brain (54). The nonspecific enzyme from several microbial sources deaminates adenosine triphosphate (ATP) and adenosine diphosphate (ADP) as well as AMP (see Section V). 

An important discovery, that of free adenylic acid in muscle, was made by Embden in 1927. Muscle adenylate was recognized as the 5 -mono-phosphoric ester of adenosine because enzymatic deamination yielded the known inosinic acid. It was shown at that time that the deaminase preparations from muscle did not deaminate the adenylic acid isolated from alkaline hydrolysates of yeast nucleic acid as well, differences were apparent in the chemical properties of the adenylic acids from these two sources. Yeast adenylic acid and the other nucleotides from alkaline hydrolysates of RNA were ultimately shown to be mixtures of the 2 - and 3 -phospho esters. In 1929 the isolation of adenosine triphosphate from muscle was reported by Lohmann and independently by Fiske and Subbarow. The discovery of adenosine diphosphate followed in 1935. 

This enzyme was discovered in rabbit muscle, and it catalyzes the irreversible deamination of adenosine-5 -phosphate and desoxyadenylic acid. Adenosine-2 -phosphate, adenosine-3 -phosphate, adenosine diphosphate, and adenosine triphosphate are not attacked. 

The 5 -adenyhc acid deaminase (22) found in rabbit muscle has been crystallized (23). It converts adenylic acid to inosinic acid and ammonia [Eq. (7)]. The enzyme does not deaminate adenine, adenosine, adenosine diphosphate, adenosine triphosphate, adenosine 2 -phosphate, adenosine S -phosphate, guanosine, or cytosine but does act upon deoxyadenylic acid (24)-... 

A relatively nonspecific adenyl deaminase has been purified from Aspergillus oryeae which deaminates, in descending order of rate, adenosine, adenosine 5 -phosphate, adenosine 3 -phosphate, ATP, adenosine diphosphate (ADP), DPN, DPNH, and adenosine-diphosphate-ribose. Adenine, TPN, and adenosine 2 -phosphate are unaltered by the enzyme (29). A... 

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