Engineering of Corynebacterium glutamicum to Enhance L-ornithine Production by Gene Knockout and Comparative Proteomic Analysis

Engineered Corynebacterium glutamicum was constructed for L-ornithine production by disrupting genes of argF and proB to prevent the flux away from L-ornithine.Effect of the inactivation of 2-oxoglutarate de-hydrogenase complex(ODHC) on L-ornithine production was also investigated.It was found that the inactivation of ODHC by knockout of the kgd gene enhanced L-ornithine production.The engineered C.glutamicum ATCC13032(ΔargFΔproBΔkgd) produced L-ornithine up to 4.78 g·L-1 from 0.24 g·L-1 of the wild-type strain.In order to understand the mechanism of L-ornithine production in C.glutamicum ATCC13032(ΔargFΔproBΔkgd) and find out new strategies for further enhancing L-ornithine production,the comparative proteome between the wild-type and the engineered strain was analyzed.L-Ornithine overproduction in the engineered strain was related to the up-regulation of the expression levels of enzymes involved in L-ornithine biosynthesis pathway and down-regulation of the expression levels of proteins involved in pentose phosphate pathway.The overexpression of genes in the upstream pathway of glutamate to increase the availability of endogenous glutamate may further in-crease ornithine production in the engineered C.glutamicum and the ornithine synthesis enzymes(ArgCJBD) may not be the limiting enzymes in the engineered C.glutamicum.

The effect of L-ornithine hydrochloride ingestion on human growth hormone secretion after strength training

This study aimed to examine the effect of L-ornithine hydrochloride ingestion on serum growth hormone secretion response after strength training in young men who did not regularly engage in high intensity exercise. Ten healthy young males without workout habits (age: 22.2 +/- 1.0 yr). Subjects performed biceps curl strength training after L-ornithine hydro- chloride and placebo ingestions. They participated in both of the above conditions randomly with a week interval in between. Serum growth hormone and ornithine levels were measured before L-ornithine hydrochloride or placebo ingestions and at 30 minutes after strength training. Serum growth hormone and ornithine level were measured. A change magnitude of serum growth hormone was significantly larger in the L-ornithine hydrochloride condition than in the placebo condition, and the effect size was also large (t = 1.91, p = .044, ES = .75). A significant interaction (F = 280.98, p = 0.000, ηp2 = 0.96) was found in serum ornithine and a multiple comparison test showed that it was greater in the L-ornithine hydrochloride condition. Serum growth hormone level after strength training increases by L-ornithine hydrochloride ingestion in untrained young males.

L-ornithine hydrochloride ingestion increased carbohydrate oxidation but not lipid oxidation during submaximal endurance exercise following resistance exercise

This study aimed to examine the effect of L-ornithine hydrochloride ingestion on lipid oxidation during submaximal endurance exercise following resistance exercise. Ten healthy young male adults with no history of regular resistance exercise (age: 26.0 +/- 4.4) conducted resistance exercise after L-ornithine hydrochloride or placebo ingestion (0.1 g/kg). Subjects exercised for 60 min on an ergometer at 50% VO2peak 120 min after resistance exercise. Plasma ornithine concentrations measured immediately, 120min and 180min after resistance exercise in the L-ornithine hydrochloride ingestion condition were significantly greater than those in the placebo condition. No significant difference was found in serum growth hor mone concentrations between both conditions (F = 4.4, p = 0.065). Serum free fatty acid concentrations were significantly greater immediately after submaximal ergometer bicycle exercise in both conditions than those before ingestion, immediately after resistance exercise and 120min after resistance exercise (F = 43.4, p .001, 300% - 508%), but no significant difference was found between both conditions (F = 3.6, p = 0.090). A similar trend was observed in serum ketone bodies as well. Although total energy production during submaximal ergometer exercise did not significantly differ (t = 0.74, p = 0.238), a significant difference was found in energy production via carbohydrate and lipid oxidation;the former was greater in the Lornithine hydrochloride ingestion condition (t = 1.89, p = 0.046, d = 0.44, 106%), and the latter was greater in the placebo condition (t = 1.89, p = 0.046, d = 0.78%, 145%). From the above, L-ornithine hydrochloride ingestion may not affect lipid metabolism during submaximal endurance exercise following resistance exercise. It may be involved in energy production via carbohydrate oxidation with glucogenic amino acid.

Super-anti-freezing,tough and adhesive titanium carbide and L-ornithine-enhanced hydrogels

Hydrogels are highly porous three-dimensional crosslinked polymer networks consisting of hy-drophilic polymers,employed most practically in medicine and industry,often as biosensors.Simple hydrogels suffer limitations in their mechanical properties,such as tensile and com-pression,and freeze at sub-zero temperatures,which compromise their ability as useful biosen-sors.In this study,the incorporation of L-ornithine-based zwitterionic monomer(OZM),titanium carbide(MXene),and glycerol within polyacrylamide hydrogels was used to prepare a novel polyacrylamide/polyL-ornithine-based zwitterion/MXene(PAM/Porn/MXene)hydrogel to im-prove the mechanical,adhesion,and anti-freezing properties of pure polyacrylamide hydrogels.This study also analyzed the mechanical strength(tensile and compression),adhesion,and anti-freezing properties of a novel PAM/Porn/MXene hydrogel at 1%,4%,and 10%MXene concen-trations to establish to what extent the conductive MXene material enhanced these properties and concluded that the tensile and compressive properties improved linearly with the increase in the concentrations of MXene,adhesion decreased with the increased MXene concentrations,and syn-ergistic interaction between MXene and OZM significantly improved the anti-freezing properties up to-80°C.

Syntheses of Macrocyclic Amides from L-Amino Acid Esters by RCM

A series of succinate-derived macrocyclic amides（1） was synthesized via ring-closing metathesis（RCM） as the key step. The substrate included 12 to 15 members. The metathesis precursors were obtained from the amide coupling of ten-butyl 3-carboxyhex-5-enoate（2） with numerous side-chain aikenylated amino acid esters of general type（3） derived from L-lysine and L-ornithine.

Evidence-based approach to management of hepatic encephalopathy in adults

Hepatic encephalopathy(HE)is a reversible syndrome of impaired brain function and represents one of the many complications of portal hypertension and decompensated liver disease.Although ammonia is clearly implicated in the pathogenesis of HE,the pathogenesis of HE is multifactorial with numerous mechanisms that results in functional impairment of neuronal cells.The initial management of HE focuses on supportive care and stabilization which includes providing appropriate nutritional support.Thereafter,focus should be on identifying and treating the precipitating factors.There are many therapeutic agents available for the management of HE,most of which are directed towards lowering the gut nitrogen load and thus the serum ammonia level.This review aims to provide an update on the conventional and emerging treatment options for HE.