Publications

• The structure and specificity of Escherichia coli maltose acetyltransferase give new insight into the LacA family of acyltransferases.

  Lo Leggio L., Dal Degan F., Poulsen P., Andersen S.M., Larsen S.

  The crystallographic three-dimensional structure of the Escherichia coli maa gene product, previously identified as a maltose O-acetyltransferase (MAT) [Brand, B., and Boos, W. (1991) J. Biol. Chem. 266, 14113-14118] has been determined to 2.15 A resolution by the single anomalous dispersion metho ... >> More

  The crystallographic three-dimensional structure of the Escherichia coli maa gene product, previously identified as a maltose O-acetyltransferase (MAT) [Brand, B., and Boos, W. (1991) J. Biol. Chem. 266, 14113-14118] has been determined to 2.15 A resolution by the single anomalous dispersion method using data from a crystal cocrystallized with trimethyllead acetate. It is shown here that MAT acetylates glucose exclusively at the C6 position and maltose at the C6 position of the nonreducing end glucosyl moiety. Furthermore, MAT shows higher affinity toward artificial substrates containing an alkyl or hydrophobic chain as well as a glucosyl unit. The presence of a long hydrophobic patch near the acceptor site provides the structural explanation for this preference. The three-dimensional structure reveals the expected trimeric left-handed parallel beta-helix structure found in all other known hexapeptide repeat enzymes. In particular, the structure shows similarities both overall and at the putative active site to the recently determined structure of galactoside acetyltransferase (GAT), the lacA gene product [Wang, X.-G., Olsen, L. R., and Roderick, S. L. (2002) Structure 10, 581-588]. The structure, together with the new biochemical data, suggests that GAT and MAT are more closely related than previously thought and might have similar cellular functions. However, while GAT is specific for acetylation of galactosyl units, MAT is specific for glucosyl units and is able to acetylate maltooligosaccharides, an important property for biotechnological applications. Structural differences at the acceptor site reflect the differences in substrate specificity. << Less

  Biochemistry 42:5225-5235(2003) [PubMed] [EuropePMC]

• Maltose transacetylase of Escherichia coli. Mapping and cloning of its structural, gene, mac, and characterization of the enzyme as a dimer of identical polypeptides with a molecular weight of 20,000.

  Brand B., Boos W.

  malQ mutants, lacking amylomaltase, cannot grown on maltose. However, when maltose is present in the medium, it can be accumulated to high internal levels. In a subsequent slow reaction, accumulated maltose becomes acetylated and leaks back into the medium. The enzyme responsible for this acetylat ... >> More

  malQ mutants, lacking amylomaltase, cannot grown on maltose. However, when maltose is present in the medium, it can be accumulated to high internal levels. In a subsequent slow reaction, accumulated maltose becomes acetylated and leaks back into the medium. The enzyme responsible for this acetylation uses acetyl-CoA as acetyl donor and can be measured in crude extracts (Boos, W., Ferenci, T., and Shuman, H. A. (1981) J. Bacteriol. 146, 725-732). The structural gene for the enzyme, which we named mac, was mapped at 10.4 min on the Escherichia coli linkage map. We cloned a 3.4-kilobase pair PstI-EcoRI DNA fragment containing the mac gene. Cell-free extracts of a strain harboring the multicopy plasmid were used to purify the maltose-transacetylating activity to apparent homogeneity. On sodium dodecyl sulfate-polyacrylamide gels the enzyme exhibited a molecular weight of 20,000. Using molecular sieve chromatography, a molecular weight of 40,000 was determined for the native enzyme. Therefore, the enzyme is a dimer of two identical subunits. At a sugar concentration of 100 mM the enzyme acetylates glucose, maltose, mannose, galactose, and fructose in decreasing relative rate of 1, 0.55, 0.20, 0.07, 0.04. Maltotriose and other oligosaccharides were acetylated with 2% of the rate determined for glucose. The Km for glucose and maltose were 62 and 90 mM, and the Vmax was 0.20 and 0.11 mmol/min x mg enzyme, respectively. << Less

  J. Biol. Chem. 266:14113-14118(1991) [PubMed] [EuropePMC]

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