title: Identification and characterization of glycation adducts on osteocalcin.
abstract: Osteocalcin is an important extracellular matrix bone protein that contributes to the structural properties of bone through its interactions with hydroxyapatite mineral and with collagen I. This role may be affected by glycation, a labile modification the levels of which has been shown to correlate with bone fragility. Glycation starts with the spontaneous addition of a sugar onto a free amine group on a protein, forming an Amadori product, and then proceeds through several environment-dependent stages resulting in the formation of an advanced glycation end product. Here, we induce the first step of this modification on synthetic osteocalcin, and then use multiple mass spectrometry fragmentation techniques to determine the location of this modification. Collision-induced dissociation resulted in spectra dominated by neutral loss, and was unable to identify Amadori products. Electron-transfer dissociation showed that the Amadori product formed solely on osteocalcin's N-terminus. This suggests that the glycation of osteocalcin is unlikely to interfere with osteocalcin's interaction with hydroxyapatite. Instead, glycation may interfere with its interaction with collagen I or another bone protein, osteopontin. Potentially, the levels of glycated osteocalcin fragments released from bone during bone resorption could be used to assess bone quality, should the N-terminal fragments be targeted.
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12182, USA; Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12182, USA.
authors.forename: Corinne J
authors.initials: CJ
authors.lastname: Thomas
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12182, USA; Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12182, USA.
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Cleland
authors.affiliation: Cornell University Biotechnology Resource Center, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics and Rehabilitation, Yale University, New Haven, CT 06520, USA.
authors.forename: Caren M
authors.initials: CM
authors.lastname: Gundberg
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12182, USA; Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12182, USA. Electronic address: vashid@rpi.edu.
authors.forename: Deepak
authors.initials: D
authors.lastname: Vashishth
mesh_terms: D000595:Amino Acid Sequence; D024042:Collagen Type I / Q000378:metabolism*; D017886:Durapatite / Q000737:chemistry / Q000378:metabolism*; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007700:Kinetics; D015675:Osteocalcin / Q000737:chemistry / Q000378:metabolism*; D053495:Osteopontin / Q000737:chemistry / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D024042:Collagen Type I; D017127:Glycation End Products, Advanced; C506895:SPP1 protein, human; D015675:Osteocalcin; D053495:Osteopontin; D017886:Durapatite
keywords: Bone; Bone matrix; Glycation; Non-collagenous protein; Osteocalcin