N6-Acetyl-L-lysine

A novel aminotransferase catalyzing the second step of lysine catabolism, the oxidative transamination of the alpha-group of N6-acetyllysine, was identified and characterized in the yeast Candida maltosa. The enzyme was strongly induced in cells grown on L-lysine as sole carbon source. Its activity was specific for both N6-acetyllysine and 2-oxoglutarate. The Km values were 14 mM for the donor, 4 mM for the acceptor and 1.7 microM for pyridoxal-5-phosphate. The enzyme had a maximum activity at pH 8.1 and 32 degrees C. Its molecular mass estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis was 55 kDa. Since the native molecular mass determined by gel filtration was 120 kDa, the enzyme is probably a homodimer.

The effect of Shouhui Tongbian Capsules(SHTB) on the endogenous metabolites of colon tissue in mice with slow transit constipation was analyzed by metabolomics methods to explore its mechanism in the treatment of constipation. ICR mice were randomly divided into normal group, model group and SHTB group according to the body weight. The mice were given diphenoxylate to establish the slow transit constipation model. Mouse carbon ink pushing rate, first defecation time and the number of defecation particles in 12 h were observed. The mouse colon tissue was separated and the mucous cells were detected by Periodic acid Schiff and Alcian blue(AB-PAS) staining. Ultra-high-performance liquid chromatography electrospray ionization orbitrap tandem mass spectrometry(UPLC-ESI-Orbitrap-MS/MS) technology was used to characterize the differences in tissue metabolism to screen out the potential different metabolites and possible metabolic pathways in colon tissue. The results indicated that SHTB could significantly shorten the first defecation time and the number of defecations, and increase the number of intestinal peristalsis and mucous cells in the colonic mucosa compared to the model mice. Metabolomics results showed that, compared with the normal group, a total of 17 potential biomarkers, including L-kynurenine, N6,N6,N6-trimethyl-L-lysine, L-formylkynurenine, N6-acetyl-L-lysine, L-phenylalanine, phenylacetaldehyde, xanthoxin, thymidine, glycyl-L-leucine, cystathionine,(R)-1-aminopropan-2-ol, deoxycytidine, gamma-glutamyl-gamma-aminobutyraldehyde, D-galactose, L-arginine, L-proline and pyruvate, were found and identified in colon tissue. Treated with SHTB, these metabolic differences tended to return to normal levels. Therefore, it could be made a conclusion that the therapeutic effect of SHTB on chronic transit constipation may be related to regulating phenylalanine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, arginine and proline metabolism, cysteine and methionine metabolism, tyrosine metabolism, arginine biosynthesis, pyruvate metabolism, glycolysis, pyrimidine metabolism, tricarboxylic acid cycle and galactose metabolism.

Despite the growing number of the vaccinated population, COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a global health burden. Obesity, a metabolic syndrome affecting one-third of the population, has proven to be a major risk factor for COVID-19 severe complications. Several studies have identified metabolic signatures and disrupted metabolic pathways associated with COVID-19, however there are no reports evaluating the role of obesity in the COVID-19 metabolic regulation. In this study we highlight the involvement of obesity metabolically in affecting SARS-CoV-2 infection and the consequent health complications, mainly cardiovascular disease. We measured one hundred and forty-four (144) metabolites using ultra high-performance liquid chromatography-quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS) to identify metabolic changes in response to SARS-CoV-2 infection, in lean and obese COVID-19 positive (n=82) and COVID-19 negative (n=24) patients. The identified metabolites are found to be mainly correlating with glucose, energy and steroid metabolisms. Further data analysis indicated twelve (12) significantly yet differentially abundant metabolites associated with viral infection and health complications, in COVID-19 obese patients. Two of the detected metabolites, n6-acetyl-l-lysine and p-cresol, are detected only among the COVID-19 cohort, exhibiting significantly higher levels in COVID-19 obese patients when compared to COVID-19 lean patients. These metabolites have important roles in viral entry and could explain the increased susceptibility of obese patients. On the same note, a set of six metabolites associated with antiviral and anti-inflammatory functions displayed significantly lower abundance in COVID-19 obese patients. In conclusion, this report highlights the plasma metabolome of COVID-19 obese patients as a metabolic feature and signature to help improve clinical outcomes. We propose n6-acetyl-l-lysine and p-cresol as potential metabolic markers which warrant further investigations to better understand their involvement in different metabolic pathways in COVID-19.