Promiscuous Transferases Malonylate Furaneol Glucoside in <i>Fragaria</i> × <i>ananassa</i>

Acylation is essential in plant metabolism, protecting metabolites from enzymatic degradation, aiding xenobiotic detoxification, and regulating cellular uptake. It also enhances the stability, solubility, and bioactivity of natural products, making it valuable for drug discovery. Since HDMF (4-hydroxy-2,5-dimethyl-3(2<i>H</i>)-furanone; Furaneol) 6'-<i>O</i>-malonyl glucoside was detected in strawberries, we hypothesized that strawberry malonyltransferases (FaMATs) acylate HDMF glucoside. Genome analysis of <i>Fragaria</i> × <i>ananassa</i> and biochemical assays identified FaMAT1C, FaMAT1S, and FaMAT4C₁/S₁ as enzymes catalyzing its malonylation, producing three isomers─likely due to keto-enol tautomerism. A screening revealed the broad substrate tolerance of FaMATs, with successful malonylation observed in 67 structurally different glycosides. Notably, FaMAT4C₁/S₁ malonylated maple furanone glucoside at the 6-OH position of the glucose moiety resulted in previously unknown metabolites. This modification stabilizes glycosides by preventing glycosidic bond cleavage by glycosidases. Understanding FaMAT function deepens insights into plant specialized metabolism and supports the development of natural product-based therapeutics.