Purification, characterization and α-glucosidase inhibitory mechanisms of rarely reported proteins found in...

The protein components from Dendrobium huoshanense could be a potential hyperglycemic agent candidate. However, the characterization and activity mechanism of these proteins have not been investigated so far. The aim of this study was to purify and identify α-glucosidase inhibitory proteins from D. huoshanense, and explore their activity mechanism in depth by multiple innovative methods. Furthermore, the hydrolysates of the proteins were prepared for guiding the application.

A 11.9 kDa protein component, PPB3-II, exhibited strong α-glucosidase inhibition (half-maximal inhibitory concentration (IC₅₀) = 34.20 ± 2.93 μg/mL). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis coupled with the National Center for Biotechnology Information (NCBI) database searches revealed PPB3-II showed similarity with protein REVEILLE 3 (ASL68814.1), photosystem II protein D1 (YP_009180171.1), and photosystem II protein D2 (YP_009180186.1). The inhibition mechanism analysis elucidated PPB3-II reversibly inhibited α-glucosidase in a mixed manner and quenched its fluorescence in an unusual static pattern. Furthermore, PPB3-II bound tightly to α-glucosidase at two binding sites with an exothermic process through the hydrogen bonds, hydrophobic interactions and salt bridges, preventing the normal catalysis of substrates. Furthermore, the hydrolysis of D. huoshanense proteins using trypsin achieved the largest degree of hydrolysis (11.31 ± 1.86%).

These findings might offer new ideas for developing proteins from D. huoshanense as novel α-glucosidase inhibitors, which could be beneficial for the development of functional foods and medicine. © 2025 Society of Chemical Industry.