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KMID : 0613820040140040636
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Journal of Life Science
2004 Volume.14 No. 4 p.636 ~ p.643
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Purification and Properties of D-Xylose Isomerase from Lactococcus sp. JK-8
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Jun Hong-Ki
Kim Suk-Young
Paik Hyung-Suk
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Abstract
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D-Xylose isomerase produced by Lactococcus sp. JK-8, isolated from kimchi, was purified 17-fold of homogeneity, and its physicochemical properties were determined. Although the N-terminal amino acid sequence of D-xylose isomerase was analysed to Ala-Tyr-Phe-Asn-Asp-Ile-Ala-Pro-Ile-Lys, it was not similar to that of Lactobacillus enzyme. The molecular weight of the purified enzyme was estimated to be 180 kDa by gel filtration, 45 kDa by SDS-PAGE and the enzyme was homotetramer. The optimum pH of the enzyme was around 7 and stable between pH 6 and 8. The optimum reaction temperature was 70℃ and stable up to 70℃ in the presence of 1 mM Mn^(2＋). Like other D-xylose isomerases, this enzyme required divalent cation, such as Mg^(2＋), Co^(2＋), or Mn^(2＋) for the activity and thermostability. Mn^(2＋) was the best activator. Substrate specificity studies showed that this enzyme was highly active on D-xylose. The enzyme had an isoelectric point of 4.8, and Km values for D-xylose was 5.9 mM.
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KEYWORD
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D-xylose isomerase, Lactococcus sp, JK-8, kimchi
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