Amino acid homologs Aminopeptidases

Apart from the immune system, there is little use for the degradation products released by the proteasome, and several peptidases exist which complete their conversion into free amino acids. One of them is tricorn peptidase, originally found in Thermoplasma cells, where it exists in the form of a giant icosahedral complex of approximately 15 MDa (Tamura et al., 1996 Walz et al., 1997). It has been shown in in vitro studies that tricorn in cooperation with an array of aminopeptidases converts oligopeptides of 8-12 residues efficiently into free amino acids (Tamura et al., 1998). Tricorn peptidase has been found in a number of archaeal and bacterial species, but it is not ubiquitous functional homologs are... 

Brevibacterium linens, a characteristic component of the surface microflora of smear-ripened varieties, has a strong proteolytic activity (Gripon et al, 1991). The extracellular proteinases secreted by a number of Br. linens strains have been partially purified (see Rattray et al, 1995). The proteinase secreted by Br. linens ATCC 9174 was purified to homogeneity by Rattray et al (1995) and found to be a serine proteinase with optimum activity at pH 8.5 and 50°C. It appears to be a trimeric enzyme with a monomeric mass of 56 kDa. The sequence of the 20 N-terminal amino acids showed no homology with the published sequences of other bacterial proteinases (Rattray 1995). Foissy (1974) reported on both intra- and extracellular proteinases but they were not studied further an extracellular aminopeptidase was purified by Foissy (1978). Sprhaug (1981) described a number of peptidase activities in cell-free extracts of Br. linens. 

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