Journal of Bacteriology, August 2000, p. 4658-4660, Vol. 182, No. 16
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Departments of Medical Genetics and Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
Received 25 May 2000/Accepted 1 June 2000
Using the human cDNA sequence corresponding to guanine deaminase,
the Escherichia coli genome was scanned using the Basic Local Alignment Search Tool (BLAST), and a corresponding 439-residue open reading frame of unknown function was identified as having 36%
identity to the human protein. The putative gene was amplified, subcloned into the pMAL-c2 vector, expressed, purified, and
characterized enzymatically. The 50.2-kDa protein catalyzed the
conversion of guanine to xanthine, having a Km
of 15 µM with guanine and a kcat of 3.2 s
1. The bacterial enzyme shares a nine-residue heavy
metal binding site with human guanine deaminase, PG[FL]VDTHIH, and
was found to contain approximately 1 mol of zinc per mol of subunit of
protein. The E. coli guanine deaminase locus is 3' from an
open reading frame which shows homology to a bacterial purine base permease.
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