An acidic β-1,3 glucanase from potato tubers appears to be patatin

A β-1,3-glucanase (GLU-40) (EC 3.2.1.39) was isolated from potato tubers (Solanum tuberosum L. cv. Huinkul). Purification was performed by anion exchange chromatography and by affinity chromatography. The following results suggested that the enzyme was, in fact, patatin: a) the molecular mass of the purified enzyme was 40 kDa, the same as that of the patatin; b) the pI of the purified enzyme was approximately 4–4.5, which corresponds to that of patatin; and c) the amino-terminal amino acid sequence and the sequence of internal peptides of the purified enzyme showed a high degree of homology to that of patatin. Patatin is known as a storage protein of the potato tuber and it has been shown to have esterase activity. However, other enzymatic activities and the function(s) of patatin are unknown. Our results suggest a new, still unknown physiological role for patatin.