The present invention relates to novel C-glycosyltransferase variants and a use thereof. The C-glycosyltransferase variants according to the present invention have improved glycosidic bond-forming ability as compared with wild-type C-glycosyltransferase, and thus can increase the glycoside production effects of polyketide groups and pseudo-natural products, particularly type I, II, III polyketide, nonribosomal peptides, phenylpropanoids, and other aromatic natural products, and thus can be useful for the preparation of a drug, a food additive, a nutritional supplement, and the like containing a C-glycoside compound as a constituent ingredient.

The present invention relates to a method for preparing -branched -hydroxy carbonyl compounds through enzymatic-catalyzed reductive aldol reaction by reacting ,-unsaturated carbonyl donors with carbonyl acceptors in the presence of a polypeptide capable of catalyzing reductive aldol reactions and a cofactor, wherein the polypeptide is an enoyl-CoA carboxylase/reductase (Ecr). The replacement of the native CO.sub.2 electrophile in enoyl-CoA carboxylases/reductases (Ecrs) by different carbonyl acceptors advantageously creates a new-to-nature biocatalytic route towards -branched -hydroxy carbonyl compounds.