Family C44
Summary for family C44
| Family type peptidase | C44.001 - amidophosphoribosyltransferase precursor (Homo sapiens), MEROPS Accession MER0003314 (peptidase unit: 12-277) |
| Content of family | Peptidase family C44 contains the self-processing precursor of amidophosphoribosyltransferase. |
| History |
Identifier created: MEROPS 5.00 (20 April 2000)
Amidophosphoribosyltransferase (EC 2.4.2.14) is synthesised with an 11-residue, N-terminal propeptide that is cleaved off autolytically. Only the precursor form of the enzyme can be regarded as a peptidase, since there is no indication that the mature enzyme hydrolyses peptide bonds, although Cys12, the nucleophile in cleavage of the propeptide, becomes the N-terminal active site residue in the amidotransferase reaction catalysed by the mature enzyme. There are several homologues of amidophosphoribosyltransferase that are synthesised in the active form, i.e. Cys1 has the amidotransferase activity, requiring only removal of an initiator methionine residue; these are regarded as non-peptidase homologues in family C44. |
| Catalytic type | Cysteine |
| Active site residues | C12 |
| Active site | Cys12, the N-terminal residue of the peptidase unit (see the Alignment), is the nucleophile in catalysis, analogous to the threonine residues that mediate self-maturation of the subunits of the proteasome in family T1. |
| Activities and specificities | The only known peptidase activity is the autolytic cleavage of the amidophosphoribosyltransferase precursor protein. |
| Molecular structure | On the basis of the three-dimensional structure of the processed form, amidophosphoribosyltransferase precursor (C44.001) was one of the first N-terminal nucleophile hydrolases to be recognised (Brannigan et al., 1995), and is placed in clan PB(C). |
| Clan | PB |
| Subclan | PB(C) |
| Basis of clan assignment | Protein fold of the peptidase unit for members of this family resembles that of archaean proteasome subunit B, the type example of clan PB. |
| Biological functions | Evidently the autolytic processing of the precursor of amidophosphoribosyltransferase makes available the catalytic activity of the transferase, but the function of the latency of the precursor is not understood, since several homologous enzymes with similar kinds of activity are synthesised already in active form. |
| Statistics for family C44 | Sequences: | 10994 |
| Identifiers: | 16 |
| Identifiers with PDB entries: | 7 |
| Downloadable files |
Sequence library (FastA format) |
| Sequence alignment (FastA format) |
| Phylogenetic tree (Newick format) |
| Peptidases and Homologues |
MEROPS ID |
Structure |
| amidophosphoribosyltransferase precursor | C44.001 | Yes |
| glutamate synthase (NADPH) large chain | C44.003 | Yes |
| ferredoxin-dependent glutamate synthase 1 (chloroplast, mitochondria) | C44.951 | - |
| glutamine-fructose-6-phosphate transaminase 1 | C44.970 | Yes |
| glucosamine-fructose-6-phosphate aminotransferase | C44.971 | Yes |
| glutamine:fructose-6-phosphate amidotransferase | C44.972 | - |
| Mername-AA144 protein | C44.973 | - |
| asparagine synthetase | C44.974 | - |
| glutamine-fructose-6-phosphate transaminase 2 | C44.975 | - |
| AsnB protein | C44.976 | Yes |
| At2g16570 (Arabidopsis thaliana) | C44.A01 | - |
| At4g38880 (Arabidopsis thaliana) | C44.A02 | - |
| At4g34740 (Arabidopsis thaliana) | C44.A03 | - |
| At4g27450 (Arabidopsis thaliana) | C44.A04 | - |
| glutamine-fructose-6-phosphate transaminase precursor (Dictyostelium discoideum) | C44.A08 | - |
| PF0204 protein (Pyrococcus furiosus ) | C44.A09 | - |
| Family C44 non-peptidase homologues | non-peptidase homologue | Yes |
| Family C44 unassigned peptidases | unassigned | Yes |
