H-Gln-AMC is a fluorogenic substrate commenly used to measure the activity of glutaminyl cyclase (QC) enzymes with Km value of 51 ± 3µM at pH 8.0 and kcat value of 5.4 ± 0.1s-1[1]. Glutaminyl cyclase (QC) catalyzes the intramolecular cyclization of N-terminal glutaminyl (Gln) and glutamyl (Glu) residues to form pyroglutamic (pGlu) peptides or proteins. Some recent findings suggest that QC can be a potential target against Alzheimer’s disease, Huntington disease and other serious neurodegenerative disease[2].
H-Gln-AMC was used as a fluorescent substrate to detect glutaminyl cyclase (QC) activity in cerebrospinal fluid (CSF) from multiple sclerosis (MS) patients. In CSF, H-Gln-AMC was catalyzed by QC to form pyroglutamyl-AMC, which was subsequently hydrolyzed by pyroglutamyl aminopeptidase to release the fluorescent product AMC. The results show a slight increase in QC activity observed in MS patients, although the difference was not significant[3]. H-Gln-AMC was used as a fluorescent substrate to measure the activity of glutaminyl cyclases (QCs) from Porphyromonas gingivalis (PgQC), Tannerella forsythia (TfQC), and Prevotella intermedia (PiQC). At a concentration of 50μM H-Gln-AMC, the catalytic activity of PgQC, TfQC, and PiQC could be accurately determined based on changes in AMC fluorescence intensity[4].
References:
[1] Schilling S, Hoffmann T, Rosche F, et al. Heterologous expression and characterization of human glutaminyl cyclase: evidence for a disulfide bond with importance for catalytic activity. Biochemistry. 2002 Sep 3;41(35):10849-57.
[2] Szaszkó M, Hajdú I, Flachner B, et al. Identification of potential glutaminyl cyclase inhibitors from lead-like libraries by in silico and in vitro fragment-based screening. Mol Divers. 2017.21:175–186
[3] Gontsarova A, Kaufmann E, Tumani H, et al. Glutaminyl cyclase activity is a characteristic feature of human cerebrospinal fluid. Clin Chim Acta. 2008 Mar;389(1-2):152-9.
[4] Taudte N, Linnert M, Rahfeld J, et al.Mammalian-like type II glutaminyl cyclases in Porphyromonas gingivalis and other oral pathogenic bacteria as targets for treatment of periodontitis. J Biol Chem. 2021 Jan-Jun:296:100263.