Enzymic synthesis of lignin precursors. Purification and properties of UDP glucose: coniferyl-alcohol glucosyltransferase from cambial sap of spruce (Picea abies L.).

UDPglucose:coniferyl-alcohol glucosyltransferase was isolated from cambial sap of spruce (Picea abies). An apparently homogeneous enzyme was obtained by a seven-step procedure including dye-ligand chromatography. The enzyme has an Mr of about 50 000 and consists of one polypeptide chain. Transferase activity is not influenced by metal ions. The enzyme shows a pronounced substrate specificity towards UDPglucose and coniferyl alcohol with Km values of respectively 220 microM and 250 microM. The only reaction product is coniferin (coniferyl alcohol 7-O-beta-D-glucopyranoside). No formation of 'isoconiferin' (coniferyl alcohol 1-O-beta-D-glucoside) was detected. The reversibility of the reaction was proved by formation of [3H]UDPglucose from [3H]UDP and coniferin in the presence of the transferase. The products UDP and coniferin inhibit the reaction noncompetitively. Product inhibition patterns are consistent with a mono-iso-ordered bibi mechanism involving two isomeric enzyme forms.