Identification of novel proteolytic forms of osteocalcin in human urine

: Ivaska KK, Hellman J, Likojarvi J, Kakonen SM, Gerdhem P, Akesson K, Obrant KJ, Pettersson K, Vaananen HK

Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE

: 2003

: Biochemical and Biophysical Research Communications

: BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS

: BIOCHEM BIOPH RES CO

: 306

: 4

: 973

: 980

: 8

: 0006-291X

DOI: https://doi.org/10.1016/S0006-291X(03)01093-3

In this study, we report the isolation and characterization of osteocalcin in human urine using mass spectrometry and N-terminal sequencing. Multiple proteolytic forms of osteocalcin were found, which consisted of 16-27 residues from the middle region of the molecule. Several fragments had residue Gly7 at the N-terminus and the most predominant was fragment 7-31. Additional fragments starting from residue Asp14 were detected in the samples of children and young adults. Immunochemical detection of urine osteocalcin fragments had a statistically significant negative correlation to bone mineral density in evaluation of urine samples from 75-year-old women. Thus, the measurement of osteocalcin fragments in urine may have potential applications in diagnostics related to disorders of bone metabolism. (C) 2003 Elsevier Science (USA). All rights reserved.