Mohammed A. Ibrahim*, June C. Serem, Megan J. Bester, Albert W. Neitz and Anabella R.M. Gaspar Pages 403 - 413 ( 11 )
Background: Peptide-based therapeutics offer a unique avenue for the development of novel agents for the treatment of diabetes mellitus including α-glucosidase inhibitors. The peptide, SQSPA, was reported to possess to α -glucosidase inhibitory activity in addition to resistance to Gastrointestinal Tract (GIT) digestion.
Methods: In this study, the in silico and in vitro structure-activity analyses of the peptide was conducted using alanine scanning to identify key amino acid residues.
Results: The alanine scanning led to four analogs viz; AQSPA, SASPA, SQAPA and SQSAA which were GIT stable. Initially, the peptides were subjected to molecular docking on human α- glucosidase and α -amylase where the binding affinities to the enzymes were in the order; AQSPA>SASPA>SQSPA>SQAPA> SQSAA and AQSPA>SQSAA>SASPA>SQSPA> SQAPA, respectively. Hydrogen bond were important for the binding of all peptides but SASPA and AQSPA had the highest hydrogen bonds interactions with the α-glucosidase and α-amylase, respectively. In vitro analysis revealed that the α -glucosidase and α-amylase inhibitory activities of the peptides were in the order AQSPA>SQSPA>SQAPA>SASPA>SQSAA and AQSPA>SASPA> SQAPA>SQSPA>SQSAA, respectively. Using inhibition kinetics, SQSPA was a mixed inhibitor of α-glucosidase while AQSPA, SQAPA and SQSAA showed non-competitive inhibition. For α- amylase inhibition, SQSPA was a non-competitive inhibitor while AQSPA and SQSAA were mixed inhibitors; SASPA and SQAPA showed uncompetitive inhibition.
Conclusion: The results indicated that P4 and Q2 are important requirements for the α-glucosidase and α-amylase inhibitory activities of the parent peptide, SQSPA. Furthermore, alanine scanning has led to the design of a novel α-glucosidase inhibitory peptide, AQSPA, with increased activities.
Alanine scanning, diabetes mellitus, disaccharidase, peptide-based therapeutics, structure-activity relationship, amino acid residues.
Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria 0002, Department of Anatomy, University of Pretoria, Pretoria 0002, Department of Anatomy, University of Pretoria, Pretoria 0002, Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria 0002, Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria 0002