Fungal Prenyltransferase AnaPT and Its F265 Mutants Catalyze the Dimethylallylation at the Nonaromatic Carbon of Phloretin.

Phloretin is widely found in fruit and shows various biological activities. Here, we demonstrate the dimethylallylation, geranylation, and farnesylation, particularly the first dimethylallylation at the nonaromatic carbon of phloretin (1) by the fungal prenyltransferase AnaPT and its mutants. F265 was identified as a key amino acid residue related to dimethylallylation at the nonaromatic carbon of phloretin. Mutants AnaPT_F265D, AnaPT_F265G, AnaPT_F265P, AnaPT_F265C, and AnaPT_F265Y were discovered to generally increase prenylation activity toward 1. AnaPT_F265G catalyzes the O-geranylation selectively at the C-2' hydroxyl group, which involves an intramolecular hydrogen bond with the carbonyl group of 1. Seven products, 1D5, 1D7-1D9, 1G2, 1G4, and 1F2, have not been reported prior to this study. Twelve compounds, 1D3-1D9, 1G1-1G3, and 1F1-1F2, exhibited potential inhibitory effects on α-glucosidase with IC50 values ranging from 11.45 ± 0.87 to 193.80 ± 6.52 µg/mL. Among them, 1G1 with an IC50 value of 11.45 ± 0.87 µg/mL was the most potential α-glucosidase inhibitor, which is about 30 times stronger than the positive control acarbose with an IC50 value of 346.63 ± 15.65 µg/mL.

Geranylation of Chalcones by a Fungal Aromatic Prenyltransferase.

Geranylated chalcones mainly exist in plants, and many of them have attracted attention because of their diverse pharmacological and biological activities. Herein, we report geranylation of eight chalcones by the Aspergillus terreus aromatic prenyltransferase AtaPT. Ten new mono-geranylated enzyme products (1G-5G, 6G1, 6G2, 7G, 8G1, and 8G2) were obtained. Most of the products are C-geranylated products with prenyl moieties at ring B. In comparison, plant aromatic prenyltransferases usually catalyze the geranylation at ring A. Therefore, AtaPT can be used complementarily for chalcone geranylation to increase the structural diversity of small molecules. In addition, seven compounds (1G, 3G, 4G, 6G1, 7G, 8G1, and 8G2) exhibited a potential inhibitory effect on α-glucosidase with the IC50 values ranging from 45.59 ± 3.48 to 82.85 ± 2.15 µg/mL. Among them, compound 7G (45.59 ± 3.48 µg/mL) was the most potential α-glucosidase inhibitor, which is about seven times stronger than the positive control acarbose (IC50 = 346.63 ± 15.65 µg/mL).