In this study, three trehalose gene clusters, treX-Y-Z, tpS1, and treS, of the acarbose-producing strain, Actinoplanes sp. SN223/29, have been identified. In particular, five trehalose synthetic genes were sequenced and characterized in detail. They were cloned and expressed in Escherichia coli BL21(DE3)pLysS using the His-tag vector pET19b. The recombinant proteins were purified by Ni2+ -nitrilotriacetic acid agarose affinity chromatography, and their functions were characterized biochemically. Both the maltooligosyltrehalose synthase (TreY-TreZ) pathway and the trehalose synthase (TreS) pathway have maximum activity at 40 degrees C and at pH 7.5 and 7.0, respectively, in 100-mM phosphate buffer. Meanwhile, the trehalose-6-phosphate synthase (TpS1) showed maximum activity at 35 degrees C and at pH 7.5 in 100 mM Tris-HCl. As a cofactor candidate, Mg2+ enhanced the activities of all three trehalose synthetic reactions significantly. TreY produced component C from acarbose by its proposed isomerase activity, but TreS did not. This study suggests that the mutation of treY can improve acarbose production by repressing component C production. Based on the data obtained in this study, a model for component C production in Actinoplanes sp. SN 223/29 is proposed.