Browsing Pathways

Methylglyoxal, also known as pyruvaldehyde, is a cytotoxic compound derived from pyruvic acid. In E. coli, there are at least eight pathways that are responsible for the detoxification of methylglyoxal. The first reaction in this pathway is the reduction of pyruvaldehyde to (S)-lactaldehyde, along with the cofactor NADH, catalyzed by 2,5-diketo-D-gluconic acid reductase subunits A and B. Following this, (S)-lactaldehyde is dehydrogenated into L-lactic acid by the lactaldehyde dehydrogenase enzyme, also using NAD as a cofactor. Finally, L-lactic acid is converted to pyruvic acid by L-lactate dehydrogenase in a reaction involving the reduction of an electron acceptor. Pyruvic acid is then used in glycolysis and pyruvate dehydrogenase pathways.

Methylglyoxal, also known as pyruvaldehyde, is a cytotoxic compound derived from pyruvic acid. In E. coli, there are at least eight pathways that are responsible for the detoxification of methylglyoxal. The first reaction in this pathway is the reduction of pyruvaldehyde to (S)-lactaldehyde, along with the cofactor NADH, catalyzed by 2,5-diketo-D-gluconic acid reductase subunits A and B. Following this, (S)-lactaldehyde is dehydrogenated into L-lactic acid by the lactaldehyde dehydrogenase enzyme, also using NAD as a cofactor. Finally, L-lactic acid is converted to pyruvic acid by L-lactate dehydrogenase in a reaction involving the reduction of an electron acceptor. Pyruvic acid is then used in glycolysis and pyruvate dehydrogenase pathways.

Methylglyoxal, also known as pyruvaldehyde, is a cytotoxic compound derived from pyruvic acid. In E. coli, there are at least eight pathways that are responsible for the detoxification of methylglyoxal. The first reaction in this pathway is the reduction of pyruvaldehyde to (S)-lactaldehyde, along with the cofactor NADH, catalyzed by 2,5-diketo-D-gluconic acid reductase subunits A and B. Following this, (S)-lactaldehyde is dehydrogenated into L-lactic acid by the lactaldehyde dehydrogenase enzyme, also using NAD as a cofactor. Finally, L-lactic acid is converted to pyruvic acid by L-lactate dehydrogenase in a reaction involving the reduction of an electron acceptor. Pyruvic acid is then used in glycolysis and pyruvate dehydrogenase pathways.

The most common pathway for methylglyoxal detoxification is the glyoxalase system, which is composed of two enzymes that together convert methylglyoxal to (R)-lactate in the presence of glutathione. However, in E. coli, a single enzyme, glyoxalase III, catalyzes this conversion in a single step without involvement of glutathione. Activity of glyoxalase III increases at the transition to stationary phase and expression is dependent on RpoS, suggesting that this pathway may be important during stationary phase. (EcoCyc)

L-lyxose is a sugar and a monosaccharide containing five carbon atoms and aldehyde group. Wild-type E.coli can't utilize L-lyxose as its source of carbon and energy. In mutated E.coli, it can metabolize l-lyxose through utilization of enzymes of the rhamnose, arabinose and 2,3-diketo-L-gulonate systems. β-L-lyxopyranose enter cell by L-rhamnose-proton symporter, then convert to l-xylulose by L-rhamnose isomerase. L-xylulose is further metabolized to L-xylulose-5-phosphate with energy ATP. Putative L-ribulose-5-phosphate 3-epimerase can convert L-xylulose -5-phosphate to L-ribulose 5-phosphate, and L-ribulose 5-phosphate 4-epimerase can catalyze L-ribulose 5-phosphate to xylulose 5-phosphate for further pentose phosphate.

The salAR operon in Acinetobacter sp. strain ADP1 is a sophisticated regulatory unit that plays a crucial role in the catabolism of salicylate, a compound that can originate from sources such as ethyl salicylate. When the concentration of salicylate in the environment reaches a high level, it acts as an inducer for the regulatory protein SalR. Upon its activation, SalR binds to the promoter region of the salAR operon, initiating the transcription of its genes. This process primarily enhances the expression of salA, which encodes salicylate hydroxylase. This enzyme catalyzes the conversion of salicylate into catechol, an important metabolic intermediate. Once produced, catechol is further processed by the catBCIJFD operon, which is integral to the subsequent degradation pathway. This operon facilitates the transformation of catechol into 3-Oxoadipate , which is then broken down into succinate. Succinate is a pivotal component that enters the tricarboxylic acid (TCA) cycle, thereby contributing to the organism’s energy production. Through this metabolic route, Acinetobacter sp. strain ADP1 not only efficiently utilizes salicylate and its derivatives as carbon sources but also integrates the breakdown products into its broader energy-generating pathways. This seamless transition from salicylate to catechol and subsequently to succinate underscores the intricacy and efficiency of metabolic regulation in responses to environmental cues, illustrating the organism's ability to adapt to diverse substrates and optimize its energy yield.

The salAR operon in Acinetobacter sp. strain ADP1 is a sophisticated regulatory unit that plays a crucial role in the catabolism of salicylate, a compound that can originate from sources such as ethyl salicylate. When the concentration of salicylate in the environment reaches a high level, it acts as an inducer for the regulatory protein SalR. Upon its activation, SalR binds to the promoter region of the salAR operon, initiating the transcription of its genes. This process primarily enhances the expression of salA, which encodes salicylate hydroxylase. This enzyme catalyzes the conversion of salicylate into catechol, an important metabolic intermediate. Once produced, catechol is further processed by the catBCIJFD operon, which is integral to the subsequent degradation pathway. This operon facilitates the transformation of catechol into 3-Oxoadipate , which is then broken down into succinate. Succinate is a pivotal component that enters the tricarboxylic acid (TCA) cycle, thereby contributing to the organism’s energy production. Through this metabolic route, Acinetobacter sp. strain ADP1 not only efficiently utilizes salicylate and its derivatives as carbon sources but also integrates the breakdown products into its broader energy-generating pathways. This seamless transition from salicylate to catechol and subsequently to succinate underscores the intricacy and efficiency of metabolic regulation in responses to environmental cues, illustrating the organism's ability to adapt to diverse substrates and optimize its energy yield.

The salDE operon in Acinetobacter sp. strain ADP1 plays a critical role in the catabolism of ethyl salicylate, enabling the bacterium to utilize this aromatic ester as a carbon source. The operon is induced by the presence of ethyl salicylate through the action of the Arer protein, an aromatic-responsive transcriptional regulator. When ethyl salicylate is present in the environment, it binds to Arer, causing a conformational change that allows Arer to activate the transcription of the salDE operon. The operon encodes two key proteins: SalD, a transporter responsible for the uptake of ethyl salicylate into the cell, and SalE, an esterase that hydrolyzes ethyl salicylate into salicylate and ethanol. The salicylate produced by SalE serves as a critical inducer for the salAR operon, which encodes enzymes that further metabolize salicylate into catechol and ultimately feeding into the TCA cycle for energy production. Thus, the salDE operon acts as a crucial link between the transport and initial breakdown of ethyl salicylate and the activation of downstream metabolic pathways, enabling the bacterium to efficiently degrade and utilize this aromatic compound. The regulatory role of Arer ensures that the operon is expressed only when ethyl salicylate is available, optimizing the cell's metabolic response to environmental conditions.