Glycine homeostasis requires reverse SHMT flux. Author Matthew McBride, Craig Hunter, Joshua Rabinowitz Publication Year 2023 Type Journal Article Abstract The folate-dependent enzyme serine hydroxymethyltransferase (SHMT) reversibly converts serine into glycine and a tetrahydrofolate-bound one-carbon unit. Such one-carbon unit production plays a critical role in development, the immune system, and cancer. Here we show that the whole-body SHMT flux acts to net consume rather than produce glycine. Pharmacological inhibition of whole-body SHMT1/2 and genetic knockout of liver SHMT2 elevated circulating glycine levels up to eight-fold. Stable isotope tracing revealed that the liver converts glycine to serine, which is then converted by serine dehydratase into pyruvate and burned in the tricarboxylic acid cycle. In response to diets deficient in serine and glycine, de novo biosynthetic flux was unaltered but SHMT2- and serine dehydratase-mediated catabolic flux was lower. Thus, glucose-derived serine synthesis does not respond to systemic demand. Instead, circulating serine and glycine homeostasis is maintained through variable consumption, with liver SHMT2 as a major glycine-consuming enzyme. Journal bioRxiv Date Published 2023/01/12 DOI 10.1101/2023.01.11.523668 Alternate Journal bioRxiv PMCID PMC9882094 PMID 36711816 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML