MipLAAO, a new L-amino acid oxidase from the redtail coral snake, Micrurus mipartitus
L-amino acid oxidases (LAAOs) are ubiquitous enzymes in nature. Bioactivities described for these enzymes include apoptosis induction, edema formation, induction or inhibition of platelet aggregation, as well as antiviral, antiparasite, and antibacterial actions. With over 80 species, Micrurus sn...
|Main Authors:||Rey Suárez, Paola, Acosta, Cristian, Torres Lamus, Uday Daniel, Saldarriaga Córdoba, Mónica María, Lomonte, Bruno, Núñez Rangel, Vitelbina|
L-amino acid oxidases (LAAOs) are ubiquitous enzymes in nature. Bioactivities
described for these enzymes include apoptosis induction, edema formation, induction
or inhibition of platelet aggregation, as well as antiviral, antiparasite, and antibacterial
actions. With over 80 species, Micrurus snakes are the representatives of the Elapidae
family in the New World. Although LAAOs in Micrurus venoms have been predicted
by venom gland transcriptomic studies and detected in proteomic studies, no enzymes
of this kind have been previously purified from their venoms. Earlier proteomic studies
revealed that the venom of M. mipartitus from Colombia contains 4% of LAAO.
This enzyme, here named MipLAAO, was isolated and biochemically and functionally
characterized. The enzyme is found in monomeric form, with an isotope-averaged
molecular mass of 59,100.6 Da, as determined by MALDI-TOF. Its oxidase activity
shows substrate preference for hydrophobic amino acids, being optimal at pH 8.0.
By nucleotide sequencing of venom gland cDNA of mRNA transcripts obtained from
a single snake, six isoforms of MipLAAO with minor variations among them were
retrieved. The deduced sequences present a mature chain of 483 amino acids, with
a predicted pI of 8.9, and theoretical masses between 55,010.9 and 55,121.0 Da. The
difference with experimentally observed mass is likely due to glycosylation, in agreement
with the finding of three putative N-glycosylation sites in its amino acid sequence.
A phylogenetic analysis of MmipLAAO placed this new enzyme within the clade
of homologous proteins from elapid snakes, characterized by the conserved Serine
at position 223, in contrast to LAAOs from viperids. MmipLAAO showed a potent
bactericidal effect on S. aureus (MIC: 2 mg/mL), but not on E. coli. The former activity
could be of interest to future studies assessing its potential as antimicrobial agent.