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L-amino acid oxidase (LAAO) is a kind of immune protease widely found in nature. In order to explore the gene sequence characteristics of LAAO (PmLAAO) and its expression changes after stimulation by Vibrio parahaemolyticus, the full-length cDNA of PmLAAO was cloned in this study. The length of its open reading frame (ORF) is 1767 bp, encoding a total of 588 amino acids, and has the structure domain of FAD-binding domain and amino acid oxidase (Amino_oxidase), which is a member of the amino acid oxidase family. The results of multiple sequence comparisons and phylogenetic trees showed that PmLAAO was closely related to bicrustacea, among which LAAO was the most similar to the Mytilus californianus. qRT-PCR results showed that PmLAAO was expressed in gill, mantle, adductor muscle, gonadal gland and digestive gland, with the highest expression level in gill tissue. After stimulation by Vp, the expression level of PmLAAO in gill tissue was significantly increased, and the expression level was the highest 48 h after stimulation. These results provide a reference for the functional activity of the novel immune protease LAAO in bivalve shellfish. [ABSTRACT FROM AUTHOR]

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Interleukin-4 induced 1 protein (IL4I1), a secreted amino acid oxidase produced by antigen presenting cells, oxidizes phenylalanine to phenylpyruvate. It has been found that IL4I1 exerts an immunosuppressive function by inhibiting the proliferation and differentiation of T cells as well as limiting the proliferation of B cells. IL4I1 is involved in host defense against infection. As a gene related to poor prognosis in cancers, IL4I1 participates in tumor immune escape. IL4I1 promotes remyelination via regulation of the different phenotypes of microglia in the autoimmune demyelinating diseases, but the detailed mechanism still remains unknown. We summarize the role and mechanism of IL4I1 in the immune regulation to provide new ideas for the treatment of infections, cancers and autoimmune diseases.

Hemorrhagic snake venom specially induces apoptosis of VEC (vascular endothelial cells). Five apoptosis-inducing proteins had been purified and characterized from crude snake venom. Two of these are L-amino acid oxidase (LAO), the others belong to metalloprotease/disintegrin family. LAO catalyzes H2O2 production by oxidizing some plasma membrane proteins of VEC, disintegrins interfere with binding of integrins with their ligands. The expression of p53 and bcl-2 increases during VEC apoptosis induced by snake venom, moreover, the mRNA of bcl-2 is spliced into two fragments. It has been proved that one of adhesion-dependent signal molecules, alphavbeta3, and one of phospholipid signal molecules, PC-PLC (phosphatidylcholine-specific phospholipase C), are involved in above apoptosis-inducing signal transudation pathway. These results throw light on finding out specific component from protein is snake venom. This component is able to induce tumor vascular endothelial cells apoptosis. This review summarized progress of research on hemorrhagic snake venoms.

L-amino acid oxidase (LAO, EC 1.4.3.2) is widely found in snake venoms and is thought to contribute to the toxicity in envenoming. By using of Sephadex G-150, DEAE-Sepharose CL-6B and FPLC Superose 12 chromatography, a protein with L-amino acid oxidase activity was purified and characterized from Agkistrodon haly Pallas venom. Its molecular mass was 57 kD as determined by SDS-PAGE analysis under both reducing and non-reducing conditions, and its pI was about 4.9. The protein catalysed the stereospecific oxidative deamination of L-amino acid substrate. It inhibited the platelet aggregation induced by ADP and collagen dose-dependently, even at low concentrations of 0.2 micromol/L and 0.08 micromol/L, respectively. The LAO had antibacterial effect to E.coli K12D31, and the effective concentration was as low as 0.03 g/L. Furthermore, the LAO showed cytotoxicity in crystal violet assay and apoptosis-inducing activity in the A549 cells. After 24h treatment with 5 mg/L LAO, the typical DNA fragmentation pattern of apoptotic cells was observed by using of agrose gel electrophoresis.

This paper reports the venom from Agkistrodon halys Pallas have inhibitory activity against fungi and E. coli by tested in a disc diffusion assay. An antibacterial component--LAO from the venom were purified to homogeneous. It had not only antibacterial effect, but L-amino acid oxidase activity. And its enzymatic specific activity was 808 U/mg. The venom had at least 3 antibacterial components (I, II, III) as determined by acid polyacrilamide gel electrophoresis, LAO is the antibaterial components II.

Members of Proteeae were vertically inoculated into different brands of sulfide-indole-motility (SIM) medium for evaluating the capability of IPA production. A total of 328 clinical strains of tribe Proteeae was used as tested organisms, including 186 Proteus mirabilis strains, 62 Morganella morganii strains, 31 Proteus vulgaris strains, 27 Providencia rettgeri strains, 14 Providencia stuartii and 8 Providencia alcalifaciens strains. Seven different brands of SIM medium used in this study are Kyokuto and Eiken from Japan; Gibco, Difco, Scott and BBL from U.S.A.; as well as Oxoid from England. The results indicate that SIM medium of kyokuto is the most suitable medium for Proteus spp. and Providencia spp. to produce IPA (positive rates are 95.4% and 93.0%, respectively) but not for Morganella morganii (16.1%). Eiken, Gibco and BBL SIM medium are only good for Providencia spp. to produce IPA (positive rates are 95.5%, 85.1% and 87.8%, respectively). Take account the tribe Proteeae the best SIM medium to detect IPA production was from Kyokuto (80%) and the worst was Oxoid (0.3%). Since SIM medium can constantly detect the production of H2S, the relationship between H2S and IPA was analyzed. We found that there is no obvious interaction between these two characters. Production of phenylalanine deaminase (PD) is one of the important characters for tribe Proteeae. We compared PD and IPA positive rates of each members and found that the ability to produce PD and IPA is almost identical for each member in tribe Proteeae except Morganella morganii.(ABSTRACT TRUNCATED AT 250 WORDS)