Aspartate, Arginine and Methionine metabolism. Aspartate aminotransferase (ASAT) catalyzes the transfer of amino groups from glutamine to oxaloacetic acid to produce aspartate and α-ketoglutaric acid. Aspartic acid is catalyzed by aspartic synthase (ASNS), and the amino group is provided by glutamine to form asparagine. Aspartic acid can participate in NAD biosynthesis by aspartic oxidase (AO). Aspartate is also involved in the synthesis of Tyrosine and Phenylalanine through its conversion to Arogenate. Aspartic acid can be transformed into Aspartate semialdehyde through aspartic kinase (AK), which further catalyzes o-phospho-l-homoserine (OPLH) to participate in Lysine, Methionine, Threonine, Synthesis of Isoleucine. Arginine in cells is catalyzed by Arginase to produce Ornithine and enter the ornithine cycle. Ornithine transcarbamylase (OTC) catalyzes the production of citrulline in mitochondria. In the cytoplasm, arginine produces citrulline and nitric oxide by nitric oxide synthase (NOS), the first step in the urea cycle. Citrulline is produced by Argininosuccinate synthase (ASS) to arginine, which is catalyzed by Argininosuccinate Lythase (ASL) to produce arginine, and the resultant fumaric acid enters the TCA cycle. In addition, ornithine in mitochondria can be converted from glutamic acid and proline. Methionine can be catalyzed by methionine adenosine transferase (MAT) to produce S-adenosine methionine (SAM). As a methyl donor, SAM participates in the methylation of histones, nucleic acids and proteins under the catalysis of methyltransferase, and produces S-homocysteine (SAH). SAH is catalyzed to produce HOMOcysteine by Adenosylhomocysteinase (AHCY), which may participate in glutathione synthesis (GSH) or in folate recycling and resynthesis of methionine via methionine synthase (MS). In the methionine remedial synthesis pathway, SAM participates in polyamine metabolism via Adenosylmethionine decarboxylase 1 (AMD1), 5,-methylthioadenosine (MTA) is produced and then phosphorylase is re-synthesized through 5-methylthioadenosine (MTAP) and the subsequent reaction. Created with BioRender.com. (The dotted line represents the intermediate process omission)
