Abstract Glycine cleavage system (GCS) occupies a key position in one-carbon (C1) metabolic pathway and receives great attention for the use of C1 carbons like formate and CO2 via synthetic biology. In this work. we demonstrate that formaldehyde exists as a substantial byproduct of the GCS reaction cycle. Three causes are identified for its formation. https://www.ngetikin.com/flash-choice-1-Gallon-Roll-Cote-High-Performance-Moisture-Vapor-Barrier-Coating-and-Primer-limited-super/