Alex K Chen Posted June 12, 2023 Report Share Posted June 12, 2023 Quote Alpha-amylase (α-amylase) is an enzyme that has a major role in carbohydrate metabolism [22], catalysing the hydrolysis of the α-(1,4) glycosidic linkages in starch and other oligosaccharides [23]. This may represent a potential mechanistic target for interventions seeking to inhibit carbohydrate uptake in the body. Indeed, bioactive ingredients that inhibit catabolic enzymes (i.e., amylase and glucosidase) are becoming increasingly popular [24], with potential applications for both weight loss and metabolic health. White kidney beans (Phaseolus vulgaris L.) possess three isoforms of α-amylase inhibitors—α-AI1, α-AI2, α-AIL [25], with the α-AI1 isoform shown to inhibit amylase activity in mammals [26]. The structure of α-AI1 is a classic lectin fold, containing no α-helices and a plethora of antiparallel β-sheets [23]. α-AI1 has no carbohydrate-binding abilities due to the complete absence of surface carbohydrate-binding loops on its three-dimensional structure [26]. Functioning optimally within a pH range of 4.5–5.5 and a temperature range of 22–37 °C [26]. α-AI1 has been suggested to interact with pancreatic α -amylase at its active site, competitively inhibiting its binding with carbohydrate [26]. α-AI1 can block the enzyme’s substrate-reducing end and obstruct the non-substrate-reducing end through a steric hindrance process, targeting all catalytically-competent components of the enzyme [22]. Several commercially-available white kidney bean extracts (WKBEs) now exist which reportedly contain high quantities of white kidney bean-derived α-amylase inhibitors, typically available in powder form, allowing their encapsulation or incorporation into drinks and foods (for further information on the preparation of these extracts, see [26]). These supplements claim to reduce carbohydrate absorption and digestion via their α-amylase inhibitory properties, with attendant beneficial effects on body weight and metabolic health. Whilst this has been the subject of two meta-analyses, one was published almost ten years ago [27] and the other focussed on a specific brand (Phase 2) [28], and other forms of WKBE might be differentially effective. Therefore, in the following section, the evidence for and against these claims is reviewed. Quote Link to comment Share on other sites More sharing options...
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