- Source: Threonine aldolase
The enzyme threonine aldolase (EC 4.1.2.5) is an enzyme that catalyzes the chemical reaction
L-threonine
⇌
{\displaystyle \rightleftharpoons }
glycine + acetaldehyde
This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is L-threonine acetaldehyde-lyase (glycine-forming). This enzyme is also called L-threonine acetaldehyde-lyase. This enzyme participates in glycine, serine and threonine metabolism. It employs one cofactor, pyridoxal phosphate.
Structural studies
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes 1JG8, 1LW4, 1LW5, 1M6S, and 1SVV.
Presence in human and mouse
The enzyme is synthesized and functional in mice.
Humans also have the remnants of the gene, coding this enzyme (GLY1), however it is damaged by past mutations and inactive. Human gene contains two single nucleotide deletions causing frameshifts and premature stop codons. Also, the encoded protein would not be active anyway due mutations in other highly conserved regions. Human gene is no longer transcribed into RNA.
References
Bell SC; Turner JM (1973). "Bacterial threonine aldolase and serine hydroxymethyltransferase enzyme". Biochem. Soc. Trans. 1 (3): 678–681. doi:10.1042/bst0010678.
KARASEK MA, GREENBERG DM (1957). "Studies on the properties of threonine aldolases". J. Biol. Chem. 227 (1): 191–205. doi:10.1016/S0021-9258(18)70806-5. PMID 13449064.
Kumagai H, Nagate T, Yoshida H, Yamada H (1972). "Threonine aldolase from Candida humicola. II. Purification, crystallization and properties". Biochim. Biophys. Acta. 258 (3): 779–90. doi:10.1016/0005-2744(72)90179-9. PMID 5017702.