Identification of New Protein Substrate Candidates of Transglutaminase in Rat Liver Extracts: Use of 5-(Biotinamido) Pentylamine as a Probe

We isolated amine acceptor protein substrates of transglutaninase in rat liver extract using of 5-(biotinamido) pentylamine as a biotin-labeling probe. Three proteins with a molecular mass of 40, 42, and 45 kDa were main components of labeled proteins. Using amino acid sequence analyses and sequence homology searches, the 40, 42, and 45 kDa proteins were identified as arginase-I (EC 3.5.3.1), fructose-1,6-bisphosphatase (EC 3.1.3.11), and betaine-homocysteine S-methyltransferase (EC 2.1.1.5), respectively. These results were also confirmed by immunoblotting analyses. Arginase-I and fructose-1,6-bisphosphatase are the new protein substrate candidates of transglutaminase, suggesting that these two enzymes can be modified post-translationally by cellular transglutaminase.