Structure and biosynthesis of the xylose-containing carbohydrate moiety of rice alpha-amylase

Abstract

Suspension-cultured cells of rice secrete alpha-amylase into the culture medium. It has been shown that the mature form of the alpha-amylase contains xylose-bearing N-linked oligosaccharide: (formula; see text) We demonstrate that suspension-cultured cells of rice secrete alpha-amylase containing oligomannose-type oligosaccharides in the presence of 1-deoxymannojirimycin or tris(hydroxymethyl)aminomethane. On the other hand, alpha-amylase purified from germinated rice seedlings contains several kinds of oligomannose-type and N-acetyllactosamine-type oligosaccharides. The processing pathway of oligosaccharide moieties in rice cells is discussed on the basis of a comparison of these oligosaccharides structures.