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Arabidopsis thaliana aminohydrolase ( At ADAL) has been shown to be involved in the metabolism of N 6 -methyl-AMP, a proposed intermediate during m 6 A-modified RNA metabolism, which can be subsequently incorporated into newly synthesized RNA by Pol II. It has been proposed that At ADAL will prevent N 6 -methyl-AMP reuse and catabolize it to inosine monophosphate (IMP). Here, we have solved the crystal structures of At ADAL in the apo form and in complex with GMP and IMP in the presence of Zn 2+ . We have identified the substrate-binding pocket of At ADAL and compared it with that for adenosine deaminase (ADA), adenine deaminase (ADE) and AMP deaminase (AMPD) from multiple species. The comparisons reveal that plant ADAL1 may have the potential ability to catalyze different alkyl-group substituted substrates.

The deamination rate of 2',3'-isopropylidene adenosine catalyzed by adenosine deaminase (ADA) from calf intestine and adenylate deaminase (AMPDA) from Aspergillus species has been evaluated and compared with that of the enzymatic reactions of adenosine, to elucidate the influence of the protecting group on enzyme activity.

Adenosine deaminase (ADA) and adenylate deaminase (AMPDA) catalyze the deamination of 2 ',3 '-O-isopropylideneadenosine-5'-carboxylic acid to the corresponding inosine derivative and dependence of the rate of enzymatic reaction on the ionization degree of the substrate has been studied at different pH values.

2 ',3 '-Isopropylidene group can be used as a molecular scaffold for the introduction of modifications at 5 ' and 1 ' positions of adenosine and these modified nucleosides are used to evaluate the biocatalytic activity of adenosine and adenylate deaminase.

In the present paper physico-chemical properties of AMP-deaminase purified from human liver neoplasm-hepatocellular carcinoma (HCC) were investigated and compared with these obtained for the enzyme from normal, unaffected tissue.