The Identification and Biochemical Properties of the Catalytic Specificity of a Serine Peptidase Secreted by Aspergillus fumigatus Fresenius
Ronivaldo Rodrigues da Silva, Renato Cesar Caetano, Debora Nona Okamoto, Lilian Caroline Goncalves de Oliveira, Thiago Carlos Bertolin, Maria Aparecida Juliano, Luiz Juliano, Arthur H. C. de Oliveira, Jose C. Rosae and Hamilton Cabral
Affiliation: Av. do Cafe, s/nº Campus Universitario da USP CEP 14040-903 Ribeirao Preto/Sao Paulo/Brazil.
Aspergillus fumigatus is a saprophytic fungus as well as a so-called opportunist pathogen. Its biochemical potential
and enzyme production justify intensive studies about biomolecules secreted by this microorganism. We describe
the alkaline serine peptidase production, with optimum activity at 50°C and a pH of 7.5 and a reduction in proteolytic activity
in the presence of the Al+3 ions. When using intramolecularly quenched fluorogenic substrates, the highest catalytic
efficiency was observed with the amino acid leucine on subsite S’3 (60,000 mM-1s-1) and preference to non-polar amino
acids on subsite S3. In general, however, the peptidase shows non-specificity on other subsites studied. According to the
biochemical characteristics, this peptidase may be an important biocatalyst for the hydrolysis of an enormous variety of
proteins and can constitute an essential molecule for the saprophytic lifestyle or invasive action of the opportunistic
pathogen. The peptidase described herein exhibits an estimated molecular mass of 33 kDa. Mass spectrometry analysis
identified the sequence GAPWGLGSISHK displaying similarities to that of serine peptidase from Aspergillus fumigatus.
These data may lead to a greater understanding of the advantageous biochemical potential, biotechnological interest, and
trends of this fungus in spite of being an opportunist pathogen.
Keywords: Aspergillus fumigatus, catalytic specificity, intramolecularly quenched fluorogenic substrates, opportunistic pathogen,
saprophytic lifestyle, serine peptidase.
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