title: Incorporation of 15N-labeled ammonia into glutamine amide groups by protein-glutaminase and analysis of the reactivity for α-lactalbumin.
abstract: Protein-glutaminase (PG) is an enzyme that catalyzes the deamidation of protein-bound glutamine residues. We found that an enzyme labeling technique (ELT), which is a stable isotope labeling method based on transglutaminase (TGase) reaction, is applicable for PG. PG catalyzed incorporation of (15)N-labeled ammonium ions into reactive glutamine amide groups in α-lactalbumin similarly to TGase and deamidated the most reactive glutamine amide group once labeled with (15)N. Furthermore, we investigated the effect of ammonium ions on the PG activity by peptide mapping, and more reactive glutamine residues were detected than were detected by the ELT in the presence of ammonium ions. This is probably because ammonium ions are competitive inhibitors, causing decreased reactivity for glutamine residues. We propose the reaction scheme of PG in the presence of the (15)N-labeled ammonium ions and show that the ELT method with PG is useful for evaluating the activity of PG.
authors: Institute of Life Science, Ajinomoto, Company, Inc, 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki-shi 210-8681, Kanagawa, Japan. noriko_miwa@ajinomoto.com
authors: Noriko
authors: N
authors: Miwa
authors: Nobuhisa
authors: N
authors: Shimba
authors: Mina
authors: M
authors: Nakamura
authors: Keiichi
authors: K
authors: Yokoyama
authors: Noriki
authors: N
authors: Nio
authors: Eiichiro
authors: E
authors: Suzuki
authors: Kenji
authors: K
authors: Sonomoto
mesh_terms: D000595:Amino Acid Sequence; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D005972:Glutaminase / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods*; D007768:Lactalbumin / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes
chemical_list: D009587:Nitrogen Isotopes; D005973:Glutamine; D000641:Ammonia; D007768:Lactalbumin; D005972:Glutaminase