Allantoicase

Description

Allantoicase (EC 3.5.3.4) participates in the uric acid degradation pathway. Its enzymatic activity, like that of urate oxidase (191540), was lost during vertebrate evolution.

Cloning and Expression

Vigetti et al. (2000) cloned the first vertebrate cDNA of allantoicase (ALLC) from the amphibian Xenopus laevis and found that its sequence showed high homology with the sequences of allantoicase in yeast. Using the sequence of the Xenopus cDNA, Vigetti et al. (2000) isolated a human ALLC cDNA from a fetal spleen cDNA library and an adult kidney EST clone. RT-PCR analysis on a panel of 7 human tissues detected an ALLC transcript in testis and, with a weaker signal, in prostate. Northern blot analysis detected a 1.8-kb signal in testis only.

Using the sequence of Xenopus allantoicase cDNA, Vigetti et al. (2001) cloned an Allc mouse cDNA encoding a hypothetical 414-amino acid protein. Northern blot analysis detected a 1.6-kb Allc transcript in testis only. RT-PCR analysis also detected Allc in testis only.

Gene Function

In mammals, the uric acid degradation pathway ends with the formation of allantoin and allantoicase activity is absent (Noguchi et al., 1979). Vigetti et al. (2000) suggested that the absence of human ALLC activity results from an incorrect splicing mechanism. Vigetti et al. (2001) hypothesized that mouse Allc mRNA remains untranslated or that the protein is synthesized, but somehow is not functional.

Evolution

Because allantoicase activity is absent not only in mammals but also in birds and reptiles, Vigetti et al. (2001) suggested that this enzymatic activity was probably lost during the colonization of the terrestrial environment by vertebrates.

Mapping

Using a somatic cell hybrid panel, Vigetti et al. (2000) mapped the human ALLC gene to chromosome 2. By database and sequence analysis, Vigetti et al. (2002) suggested that the gene is located at 2p25. They stated that the mouse Allc gene maps to chromosome 12.

Gene Structure

Vigetti et al. (2002) determined that the structure of the mouse and human ALLC gene is well conserved. Both genes are approximately the same size and contain 11 exons.