Deoxyguanylate kinase

ATP GMP phosphotransferase GMP kinase deoxyguanylate kinase guanosine monophosphate kinase kinase, guanylate (phosphorylating)... 

Guanylate kinase has been partly purified from hog brain 10), from Escherichia coli 11), and from a transplantable mouse tumor, Sarcoma 180 12). These preparations show similarities with respect to substrate specificity and cation requirements, but differ with respect to pH optima and molecular weight. All three preparations are highly specific in that guanylate and deoxyguanylate are phosphorylated, but adenylate, ino-sinate, xanthylate, and cytidylate are not substrates. The brain and tumor enzymes also phosphorylate 8-azaguanylate. ATP or dATP are the specific phosphate donors for the three enzymes. 

The acceptability of deoxyguanylate and dATP as substrates in the guanylate kinase reaction is noteworthy there does not appear to be a particular group of nucleoside monophosphate kinases specific for deoxyribonucleotides (see Chapter 14), apart from that for thymidylate and deoxyuridylate. 

Fractionation of extracts from calf thymus for kinase activity toward deoxyribonucleoside monophosphates has revealed the presence of at least four separate enzymes the kinase activities for dAMP, dGMP, dCMP, and dTMP are separate entities in this tissue 31). Each has been partly purified and examination of substrate specificities showed that the kinases for deoxyadenylate and deoxyguanylate also phosphorylate the ribosyl homologues, adenylate and guanylate, respectively. The deoxycytidylate kinase accepts as substrates both cytidylate and uridylate, but will not phosphor> late deoxyuridylate. The calf thymus thymidine monophosphate... 

As a further instance of a dual function for the nucleoside monophosphate kinases, separate kinases for adenylate-deoxyadenylate, guanylate-deoxyguanylate, cytidylate-deoxycytidylate, uridylate, and thynudylate have been demonstrated in E. cdi extracts (35) it should be noted that cytidylate-deoxycytidylate kinase and uridylate kinase were found as separate enzyme activities in the E. cdi experiments. 

Another instance of the induction of enzymes not ordinarily present in E. coli which occurs upon infection with bacteriophage T2 (see Section I, D and II, E) is found in the work of Bello and Bessman ( 4), who isolated from T2-infected E. coli, a deoxynucleoside monophosphate kinase with specificities quite distinct from those of the kinases discussed above. The phage-induced kinase is specific for deoxj/ribonucleoside monophosphates and will phosphorylate three of the four nucleotides destined for phage DNA deoxyguanylate, thymidylate, and hydroxymethyldeoxycyti-dylate. The enzyme does not phosphorylate deoxyadenylate. 

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