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Unusual properties of the prespore‐specific enzyme, UDPgalactose:polysaccharide galactosyl transferase, of Dictyostelium discoideum
Author(s) -
Nakahara Yasuo,
Okamoto Koji
Publication year - 2004
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.200410380
Subject(s) - dictyostelium discoideum , enzyme , isoelectric point , sepharose , chemistry , transferase , biochemistry , enzyme assay , molecular mass , specific activity , gene
UDPgalactose:polysaccharide galactosyl‐transferase is the enzyme that is specifically localized in prespore cells of Dictyostelium discoideum and its activity sharply changes in response to differentiation and dedifferentiation. To clarify the nature of this enzyme, we first developed an improved assay method for the enzyme, and by using this method, we partially purified the enzyme through DEAE‐sepharose, phenyl‐sepharose and ATP‐sepharose chromatography. The apparent molecular mass of the enzyme was ca. 200 KDa (by non‐denaturing polyacrylamide gel gradient analysis) and the isoelectric point was around pH 7. The enzyme exhibited a hitherto undescribed property, that is the reaction proceeds faster at 0 °C than at 21 °C, with a smaller K m value and an unchanged V max value. This low‐temperature resistant property of the enzyme is consistent with the previous observation ( Maeda 1984, J. Cell Sci. 69, 159–165) that prespore differentiation is favored at low temperatures. The reaction appears to proceed in a double displacement manner. ATP reversibly inhibited the enzyme with a K i value of 2 m M , suggesting the possibility that ATP regulates its activity in vivo . (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)