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In the process of gene mining for novel α-L-arabinofuranosidases (AFs), the gene Celf_3321 from Cellulomonas fimi ATCC 484 encodes an AF, termed as AbfCelf, with potent activity, 19.4 U/mg under the optimum condition, pH 6.0 and 40 °C. AbfCelf can hydrolyze α-1,5-linked oligosaccharides, sugar beet arabinan, linear 1,5-α-arabinan, and wheat flour arabinoxylan, which is partly different from some previously well-characterized GH 51 AFs. The traditional substrate-specificity analysis for AFs is labor-consuming and money costing, because the substrates include over 30 kinds of various 4-nitrophenol (PNP)-glycosides, oligosaccharides, and polysaccharides. Hence, a preliminary structure and mechanism based method was applied for substrate-specificity analysis. The binding energy (ΔG, kcal/mol) obtained by docking suggested the reaction possibility and coincided with the experimental results. AbfA crystal 1QW9 was used to test the rationality of docking method in simulating the interaction between enzyme and substrate, as well the credibility of the substrate-specificity analysis method in silico.

Natural small peptides from foods have been proven to be efficient inhibitors of Angiotensin I-converting enzyme (ACE) for the regulation of blood pressure. The traditional ACE inhibitory peptides screening method is both time consuming and money costing, to the contrary, virtual screening method by computation can break these limitations. We establish a virtual screening method to obtain ACE inhibitory peptides with the help of Libdock module of Discovery Studio 3.5 software. A significant relationship between Libdock score and experimental IC(50) was found, Libdock score = 10.063 log(1/IC(50)) + 68.08 (R(2) = 0.62). The credibility of the relationship was confirmed by testing the coincidence of the estimated log(1/IC(50)) and measured log(1/IC(50)) (IC(50) is 50% inhibitory concentration toward ACE, in μmol/L) of 5 synthetic ACE inhibitory peptides, which was virtual hydrolyzed and screened from a kind of seafood, Phascolosoma esculenta. Accordingly, Libdock method is a valid IC(50) estimation tool and virtual screening method for small ACE inhibitory peptides.

Recent studies have investigated anti-hypertensive peptides derived from natural food products. In this work, we focus on Phascolosoma esculenta as a resource of anti-hypertensive peptides, which is also a seafood with high nutritive value. Compared with FAO/WHO requirements, P. esculenta was confirmed to contain high contents of amino acids and minerals. To investigate the anti-hypertensive activity of P. esculenta, water-soluble and insoluble proteins were extracted and hydrolysed by pepsin and trypsin, respectively. The hydrolysates of water-soluble proteins derived by pepsin and pepsin-trypsin exhibited angiotensin-converting enzyme (ACE) inhibitory activity with IC50 values of 0.67 and 0.24 mg ml(-1), respectively, and those of water-insoluble proteins presented IC50 values of 0.4 and 0.1 mg ml(-1), respectively. Experiments on 'spontaneously hypertensive rats' (SHRs) were carried out to test the anti-hypertension activity in vivo, which confirmed that the hydrolysates played a significant role in reducing both diastolic blood pressure (DBP) and systolic blood pressure (SBP). Consistently, the in vivo anti-hypertensive activity of the hydrolysis products of pepsin and trypsin used together was also higher than that by using pepsin hydrolysis products alone. As stated in both sets of results, we believe that P. esculenta is an excellent resource of antihypertensive peptides and warrants further investigation.