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Fermentative Production of Vitamin B6
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Jonathan Rosenberg, Björn Richts, Fabian M. Commichau
The DXP-independent vitamin B6 biosynthetic pathway is much shorter because it involves only the PdxST enzyme complex, consisting of 12 PdxS and 12 PdxT subunits (Ehrenshaft and Daub, 2001; Belitsky, 2004b; Burns et al., 2005; Raschle et al., 2005; Strohmeier et al., 2006). PdxT is a glutaminase that converts glutamine to glutamate and ammonium, of which the latter serves as a substrate for the PLP synthase PdxS (Belitsky, 2004b). PdxS catalyses the reaction from ribulose 5-phosphate (Ru5P) and G3P to PLP. Due to triose and pentose isomerase activity, it can use either Ru5P or ribose 5-phosphate (Ri5P) together with either G3P or dihydroxyacetone phosphate (DHAP). Thus, the PdxS enzyme complex unifies three enzymatic activities: triose isomerase and pentose isomerase activity as well as imine formation activity for PLP synthesis (Burns et al., 2005). Even though the DXP-independent vitamin B6 pathway has been discovered a few years ago, it is more abundant in nature than the DXP-dependent route. It is present in archaea, bacteria, fungi, plants, and Plasmodium and in the sponge Suberites domuncula (Seack et al., 2001; Ehrenshaft and Daub, 2001; Fitzpatrick et al., 2007; Guédez et al., 2012; Rosenberg et al., 2017). Moreover, the DXP-independent vitamin B6 pathway emerged earlier and it has been lost several times in the course of evolution (Tanaka et al., 2005).
Biocatalyzed Synthesis of Antidiabetic Drugs
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Recently, the use of smart E. coli synthetic factory for synthesizing iminosugars have been described (Wei et al., 2015), through the transformation of DHAP-dependent aldolase-mediated in vitro reactions into engineered E. coli for facile and effective production of polyhydroxylated molecules (Fig. 11.43, 125). In glycolysis, glucose is converted into fructose 1,6-bisphosphate via three enzymatic steps and subsequently split by FruA into two interconvertible triose phosphates, DHAP and d-glyceraldehyde-3-phosphate (GAP), in a concentration ratio of DHAP to GAP is 96% to 4% because of the favored formation of DHAP by triose-phosphate isomerase (TIM). Thus, these authors introduced and overexpressed an aldolase gene and a phosphatase gene in E. coli cells, generating a synthetic factory named E. coli FruA-Y, so that the overexpressed aldolase could hijack DHAP from the glycolytic pathway and couple it with exogenous aldehyde 124 to furnish a phosphorylated aldol adduct, which is in situ dephosphorylated by the overexpressed phosphatase and released from the host cell to give the desired product (Fig. 11.43). Scheme of the modified glycolysis by an E. coli synthetic factory.
Technical Advancement for Retention of Probiotic Count During Spray-Drying Process
Published in M. Selvamuthukumaran, Handbook on Spray Drying Applications for Food Industries, 2019
As a result of heat application to probiotic microorganisms, some changes occur in the inside and outside properties of the cell. Heat treatment provides adaptation of the cell membrane by increasing the optimal fluidity of the membrane, saturation, and the length of fatty acids (Meng et al., 2008). Another mechanism of heat treatment is the accumulation of heat shock proteins, which support the translocation of intracellular proteins by preventing complexation and degradation of these proteins (Meng et al., 2008). The most well-known heat shock proteins are GroEL and GroES and they are expressed in cytoplasmic membrane under heat-adapted conditions. The accumulation of these two proteins in intracellular membrane leads to the increase of the probiotic microorganism survivability during spray drying (Ananta and Knorr, 2003; Meng et al., 2008). Desmond et al. (2001) reported that there was a considerable amount of GroEL increase in the heat-exposed cells of L. lactis. Whitaker and Batt (1991) reported that there were nearly 17 different proteins induced, when mild heat treatment was applied to E. coli cells. Besides heat shock proteins some other enzymes may also be induced after heat treatment. Prasad et al. (2003) reported that the concentration of glyceraldehyde-3-phosphate dehydrogenase and triose phosphate isomerase increased by 2.5 and 5-fold, respectively after heat treatment.
Methylglyoxal induced advanced glycation end products (AGE)/receptor for AGE (RAGE)-mediated angiogenic impairment in bone marrow-derived endothelial progenitor cells
Published in Journal of Toxicology and Environmental Health, Part A, 2018
Jeong-Hyeon Kim, Kyeong-A Kim, Young-Jun Shin, Haram Kim, Arshad Majid, Ok-Nam Bae
Methylglyoxal (MG), a highly reactive α-oxoaldehyde, is generated by nonenzymatic fragmentation of triose phosphates produced during glycolysis (Thornalley 1996). It was reported that plasma levels of MG were elevated in diabetic patients (Han et al. 2007; Lapolla et al. 2003). MG produces an advanced glycation end products (AGE), resulting from binding with the arginine residue of the protein, and the most common MG-derived AGE form is MG-derived hydroimidazolone-1 (MG-H1) (Thornalley et al. 2003). Receptors for AGE (RAGEs) play a key role in AGE signaling, particularly recognizing MG-H1 (Goldin et al. 2006; Xue et al. 2014). Enhanced formation of AGE enhances the risk of CVD complications in diabetic conditions (Bodiga, Eda, and Bodiga 2014; Cooper 2004; Hanssen et al. 2015). Further, Chen et al. (2009); Chen et al. (2010)) noted that AGE induced EPC dysfunction by increasing oxidative stress, promoting apoptosis, and inhibiting migration and blood vessel tube formation. Although evidence that AGE might contribute to EPC dysfunction was reported, it has not been demonstrated yet whether MG, a diabetic metabolite, might affect AGE formation and consequent functional impairment in EPC. In addition, the relationship between AGE formation and vascular endothelial growth factor (VEGF) signaling, which acts as a key homing signal in angiogenic functions of EC and EPC, remains to be established (Piperi et al. 2015). The aim of this study was thus to investigate the molecular mechanisms underlying endothelial dysfunction observed in diabetes by using MG-induced angiogenic impairment as a model and examining involvement of AGEs/RAGE pathway in EPC.