Browsing Pathways

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.

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.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

Phospholipids are membrane components in E. coli. The major phospholipids of E. coli are phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. All phospholipids contain sn-glycerol-3-phosphate esterified with fatty acids at the sn-1 and sn-2 positions. The reaction starts from a glycerone phosphate (dihydroxyacetone phosphate) produced in glycolysis. The glycerone phosphate is transformed into an sn-glycerol 3-phosphate (glycerol 3 phosphate) by NADPH-driven glycerol-3-phosphate dehydrogenase. sn-Glycerol 3-phosphate is transformed to a 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid). This can be achieved by an sn-glycerol-3-phosphate acyltransferase that interacts either with a long-chain acyl-CoA or with an acyl-[acp]. The 1-acyl-sn-glycerol 3-phosphate is transformed into a 1,2-diacyl-sn-glycerol 3-phosphate (phosphatidic acid) through a 1-acylglycerol-3-phosphate O-acyltransferase. This compound is then converted into a CPD-diacylglycerol through a CTP phosphatidate cytididyltransferase. CPD-diacylglycerol can be transformed either into an L-1-phosphatidylserine or an L-1-phosphatidylglycerol-phosphate through a phosphatidylserine synthase or a phosphatidylglycerophosphate synthase, respectively. The L-1-phosphatidylserine transforms into L-1-phosphatidylethanolamine through a phosphatidylserine decarboxylase. On the other hand, L-1-phosphatidylglycerol-phosphate gets transformed into an L-1-phosphatidyl-glycerol through a phosphatidylglycerophosphatase. These 2 products combine to produce a cardiolipin and an ethanolamine. The L-1 phosphatidyl-glycerol can also interact with cardiolipin synthase resulting in a glycerol and a cardiolipin.

Phospholipids are membrane components in E. coli. The major phospholipids of E. coli are phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. All phospholipids contain sn-glycerol-3-phosphate esterified with fatty acids at the sn-1 and sn-2 positions. The reaction starts from a glycerone phosphate (dihydroxyacetone phosphate) produced in glycolysis. The glycerone phosphate is transformed into an sn-glycerol 3-phosphate (glycerol 3 phosphate) by NADPH-driven glycerol-3-phosphate dehydrogenase. sn-Glycerol 3-phosphate is transformed to a 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid). This can be achieved by an sn-glycerol-3-phosphate acyltransferase that interacts either with a long-chain acyl-CoA or with an acyl-[acp]. The 1-acyl-sn-glycerol 3-phosphate is transformed into a 1,2-diacyl-sn-glycerol 3-phosphate (phosphatidic acid) through a 1-acylglycerol-3-phosphate O-acyltransferase. This compound is then converted into a CPD-diacylglycerol through a CTP phosphatidate cytididyltransferase. CPD-diacylglycerol can be transformed either into an L-1-phosphatidylserine or an L-1-phosphatidylglycerol-phosphate through a phosphatidylserine synthase or a phosphatidylglycerophosphate synthase, respectively. The L-1-phosphatidylserine transforms into L-1-phosphatidylethanolamine through a phosphatidylserine decarboxylase. On the other hand, L-1-phosphatidylglycerol-phosphate gets transformed into an L-1-phosphatidyl-glycerol through a phosphatidylglycerophosphatase. These 2 products combine to produce a cardiolipin and an ethanolamine. The L-1 phosphatidyl-glycerol can also interact with cardiolipin synthase resulting in a glycerol and a cardiolipin.

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.