The Nudix hydrolases of Deinococcus radiodurans

All 21 of the Nudix hydrolase genes from the radiation-resistant organism D einococcus radiodurans have been cloned into vectors under the control of T 7 promoters and expressed as soluble proteins in Escherichia coli. Their si zes range from 9.8 kDa (91 amino acids) to 59 kDa (548 amino acids). Two no vel proteins were identified, each with two Nudix boxes in its primary stru cture, unique among all other known Nudix hydrolases. Extracts of each of t he expressed proteins were assayed by a generalized procedure that measures the hydrolysis of nucleoside diphosphate derivatives, and several enzymati c activities were tentatively identified. In addition to representatives of known Nudix hydrolase subfamilies active on ADP-ribose, NADH, dinucleoside polyphosphates or (deoxy)nucleoside triphosphates, two new enzymes, a UDP- glucose pyrophosphatase and a CoA pyrophosphatase, were identified.