Human allantoicase gene: cDNA cloning, genomic organization and chromosomelocalization

Uric-acid-degrading enzymes (uricase, allantoinase, allantoicase, ureidogly colate lyase and urease) were lost during vertebrate evolution and the caus es for this loss are still unclear. We have recently cloned the first verte brate allantoicase cDNA from the amphibian Xenopus laevis. Surprisingly, we have found some mammalian expressed sequence tags (ESTs) that show high si milarity with Xenopus allantoicase cDNA. From a human fetal spleen cDNA lib rary and adult kidney EST clone, we have obtained a 1790 nucleotide long cD NA. The 3' end of this sequence reveals a substantial high identity with th e corresponding portion of Xenopus allantoicase cDNA. In contrast, at the 5 ' end the human sequence diverges from that of Xenopus; since no continuous open reading frame can be found in this region, the hypothetical human pro tein appears truncated at its N-terminus. We proposed that such a transcrip t could be due to an incorrect splicing mechanism that introduces an intron portion at the 5' end of human cDNA. Allantoicase cDNA is expressed in adu lt testis, prostate, kidney and fetal spleen. By comparison with available genomic sequences deposited in database, we have determined that the human allantoicase gene consists of five exons and spans 8 kb. We have also mappe d the gene in chromosome 2. (C) 2000 Elsevier Science B.V. All rights reser ved.