Taxonomic distribution of proteins containing AICARFT_IMPCHas domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing AICARFT_IMPCHas domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Molecular cloning and expression of a rat cDNA encoding 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase.

Akira T, Komatsu M, Nango R, Tomooka A, Konaka K, Yamauchi M, Kitamura Y, Nomura S, Tsukamoto I
Gene. 1997; 197: 289-93

The cDNA of a 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (AICARFT/IMPCHase) was isolated from rat liver RNA by reverse transcription and the polymerase chain reaction (PCR). The rat AICARFT/IMPCHase cDNA included 1928 bp containing a coding region of 1779 bp for a 592-amino acid polypeptide (Mr = 64 200). Rat and human AICARFT/IMPCHase cDNAs show 84 and 91% homology at the nucleotide and amino acid sequence level, respectively. The protein produced by the rat cDNA using pET-expression system catalysed the penultimate and final steps of de novo purine biosynthesis. Northern analysis identified a 2.8-kb AICARFT/IMPCHase mRNA and the level of the AICARFT/IMPCHase transcripts increased markedly at 24 h after partial (70%) hepatectomy.

The human purH gene product, 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase. Cloning, sequencing, expression, purification, kinetic analysis, and domain mapping.

Rayl EA, Moroson BA, Beardsley GP
J Biol Chem. 1996; 271: 2225-33

We report here the cloning and sequencing of the cDNA, purification, steady state kinetic analysis, and truncation mapping studies of the human 5-aminoimidazole- 4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (AICARFT/IMPCHase). These steps of de novo purine biosynthesis, respectively. In all species of both prokaryotes and eukaryotes studied, these two activities are present on a single bifunctional polypeptide encoded on the purH gene. The human purH cDNA is 1776 base pairs in length encoding for a 591-amino acid polypeptic (Mr = 64,425). The human and avian purH cDNAs are 75 and 81% similar on the nucleotide and amino acid sequence level, respectively. The Km values for AICAR and (6R,6S)10-formyltetrahydrofolate are 16.8 microM +/- 1.5 and 60.2 microM +/- 5.0, respectively, for the cloned, purified human enzyme. A 10-amino acid sequence within the COOH-terminal portion of human AICARFT/IMPCHase has some degree of homology to a previously noted "folate binding site." Site directed mutagenesis studies indicate that this sequence plays no role in enzymatic activity. We have constructed truncation mutants which demonstrate that each of the two enzyme activities can be expressed independent of the other. IMPCHase and AICARFT activities are located within the NH2-terminal 223 and COOH-terminal 406 amino acids, respectively. The truncation mutant possessing AICARFT activity displays steady state kinetic parameters identical to those of the holoenzyme.