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Locally isolated yeasts from Malaysia: Identification, phylogenetic study and characterization

100%

Oslan S. N., Salleh A. B., Rahman R. N. Z. R. A., Basri M., Chor A. L. T.

2012

vol. 59

issue 2

225-229

Yeasts are a convenient platform for many applications. They have been widely used as the expression hosts. There is a need to have a new yeast expression system to contribute the molecular cloning demands. Eight yeast isolates were screened from various environment sources and identified through ribosomal DNA (rDNA) Internal Transcribed Spacer (ITS). Full sequence of the rDNA ITS region for each isolate was BLASTed and phylogenetic study was constructed by using MEGA4. Among the isolates, isolate WB from 'ragi' (used to ferment carbohydrates) could be identified as a new species in order Saccharomycetales according to rDNA ITS region, morphology and biochemical tests. Isolate SO (from spoiled orange), RT (rotten tomato) and RG (different type of 'ragi') were identified as Pichia sp. Isolates R1 and R2, S4 and S5 (from the surrounding of a guava tree) were identified as Issatchenkia sp. and Hanseniaspora sp., respectively. Geneticin, 50 µg/mL, was determined to be the antibiotic marker for all isolates excepted for isolates RT and SO which used 500 µg/mL and 100 µg/mL Zeocin, respectively. Intra-extracellular proteins were screened for lipolytic activity at 30°C and 70°C. Thermostable lipase activity was detected in isolates RT and R1 with 0.6 U/mg and 0.1 U/mg, respectively. In conclusion, a new yeast-vector system for isolate WB can be developed by using phleomycin or geneticin as the drugs resistance marker. Moreover, strains RT and R1 can be investigated as a novel source of a thermostable lipase.

Characterisation and molecular dynamic simulations of J15 asparaginase from Photobacterium sp. strain J15

86%

Yaacob M., Hasan W., Ali M., Rahman R., Salleh A., Basri M., Leow T.

2014

vol. 61

issue 4

745-752

Genome mining revealed a 1011 nucleotide-long fragment encoding a type I l-asparaginase (J15 asparaginase) from the halo-tolerant Photobacterium sp. strain J15. The gene was overexpressed in pET-32b (+) vector in E. coli strain Rosetta-gami B (DE3) pLysS and purified using two-step chromatographic methods: Ni2+-Sepharose affinity chromatography and Q-Sepharose anion exchange chromatography. The final specific activity and yield of the enzyme achieved from these steps were 20 U/mg and 49.2%, respectively. The functional dimeric form of J15-asparaginase was characterised with a molecular weight of ~70 kDa. The optimum temperature and pH were 25°C and pH 7.0, respectively. This protein was stable in the presence of 1 mM Ni2+ and Mg2+, but it was inhibited by Mn2+, Fe3+ and Zn2+ at the same concentration. J15 asparaginase actively hydrolysed its native substrate, l-asparagine, but had low activity towards l-glutamine. The melting temperature of J15 asparaginase was ~51°C, which was determined using denatured protein analysis of CD spectra. The Km, Kcat, Kcat/Km of J15 asparaginase were 0.76 mM, 3.2 s-1, and 4.21 s-1 mM-1, respectively. Conformational changes of the J15 asparaginase 3D structure at different temperatures (25°C, 45°C, and 65°C) were analysed using Molecular Dynamic simulations. From the analysis, residues Tyr24, His22, Gly23, Val25 and Pro26 may be directly involved in the 'open' and 'closed' lid-loop conformation, facilitating the conversion of substrates during enzymatic reactions. The properties of J15 asparaginase, which can work at physiological pH and has low glutaminase activity, suggest that this could be a good candidate for reducing toxic effects during cancer treatment.

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2 Acta Biochimica Polonica

1 2014

1 2012

2 Basri M.

1 Ali M.

1 Chor A. L. T.

1 Hasan W.

1 Leow T.

1 Oslan S. N.

1 Rahman R.

1 Rahman R. N. Z. R. A.

1 Salleh A.

1 Salleh A. B.

1 Yaacob M.

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Locally isolated yeasts from Malaysia: Identification, phylogenetic study and characterization

Characterisation and molecular dynamic simulations of J15 asparaginase from Photobacterium sp. strain J15