Phylogenetic analysis of leucine aminopeptidase (LAP) in the Ascomycota

Leucine aminopeptidase (LAP, EC 3.4.11.1) is an exopeptidase, which removes the N-terminal L-leucine from peptide substrates. LAPs of aspergilli are of interest in the soybean fermentation industry because of their debittering activity. Through genomic analysis of Aspergillus sojae SMF 134 isolated from the Korean traditional soybean brick, meju, we identified three LAPs in A. sojae. By using these identified LAP genes as the query, we analyzed the published Ascomycota genomes for lap genes. Most of Ascomycota including Pezizomycotina and Saccharomycotina have one or two LAPs, however, Aspergillus spp. have three LAPs. Based on the amino acid sequences, Ascomycota LAPs can be divided into four distinct clades, with two clades in Pezizomycotina and two in Saccharomycotina, respectively. LAP1 and LAP2 are divided into separate clades in each Pezizomycotina and Saccharomycotina. LAP3 of Aspergillus sp. belong to the same clade as the LAP1 clade of Pezizomycotina. We find that all LAPs contain 15 highly conserved amino acids sequences in the major domain of LAP, suggesting that the conserved amino acids play an important role in LAP function. This analysis will provide the basis for biochemical studies of LAP with purpose of aspergilli application in industry.