Involved in plants secondary metabolism. Functions as acyltransferase to form the sinapate ester sinapoylcholine also known as sinapine. Able to convert in vitro benzoylglucose into benzoylcholine. 1-O-(trans-sinapoyl)-beta-D-glucose + choline = D-glucose + O-sinapoylcholine Slightly inhibited by phenylmethylsulfonyl fluoride (PMSF). Measured in vitro at pH 7.0 and 30 degrees Celsius. Heterodimer. Expressed in roots and flowers, and at lower levels in young leaves and seedlings. Expressed in mature seeds and detected in expanding siliques. N-glycosylated. Plants accumulate sinapoylglucose and contain low levels of sinapoylcholine and increased levels of choline. Decreased levels of both benzoylated and sinapoylated glucosinolates. Belongs to the peptidase S10 family. Was classified as a serine carboxypeptidase-like (SCPL) protein solely on the basis of the overall sequence similarity (PubMed:15908604) but it has been shown that it belongs to a class of enzymes that catalyze acyltransferase reactions (PubMed:17600138).