High-efficient preparation of ß-nicotinamide mononucleotides by crude enzymes cascade catalytic reaction.

ß-nicotinamide mononucleotide (ß-NMN) is a key precursor of nicotinamide adenine dinucleotide, and becomes attractive in the nutrition and health care fields, but its enzymatic synthesis is expensive. In this study, a six-enzyme cascade catalytic system was constructed to produce ß-NMN. Using D-ribose and nicotinamide as substrates, the ß-NMN yield reached 97.5 % catalyzed by purified enzymes. Then, after knocking out the genes encoding proteins that consume ß-NMN in E. coli BL21(DE3), the similar ß-NMN yield, 97.2 %, using the crude enzymes could be also obtained. After that, ß-NMN synthesis was performed under increased substrate concentration, and 'modular' crude enzymes cascade catalytic reaction system was proposed to reduce the inhibition of polyphosphate on ribose-phosphate diphosphokinase activity, and the ß-NMN yield reached 78.4 % at 10 mM D-ribose, which is 1.82 times of that in 'one-pot' reaction and represents the highest ß-NMN preparation level with phosphoribosylpyrophosphate as the core reported till now.

Identification and virtual screening of novel salty peptides from hydrolysate of tilapia by-product by batch molecular docking.

Introduction: Tilapia produces a large number of by-products during processing, which contain potentially flavorful peptides. Methods: The application of PyRx software enabled batch molecular docking andscreening of 16 potential salty peptides from 189 peptides identified in the enzymaticdigestion of tilapia by-products. Results: According to sensory analysis, all 16 peptides werepredominantly salty with a threshold of 0.256 - 0.379 mmol/L with some sournessand astringency, among which HLDDALR had the highest salty intensity, followedby VIEPLDIGDDKVR, FPGIPDHL, and DFKSPDDPSRH. I addition, moleculardocking results showed these four core peptides with high salt intensity bound to thesalt receptor TRPV1 mainly via van der Waals interactions, hydrogen bonds, andhydrophobic forces; Arg491, Tyr487, VAL441, and Asp708 were the key sites for thebinding of salty peptides to TRPV1. Therefore, the application of batch moleculardocking using PyRx is effective and economical for the virtual screening of saltypeptides.