Skeletal mineralisation “Hypotheses” article – accepted by FASEB J

Matrix mineralization is the process by which the skeleton forms and is maintained. Matrix vesicles (MVs) released from osteoblasts and chondrocytes serve to accumulate calcium and inorganic phosphate such that mineralization can take place. In a paper to be published in the FASEB Journal, the Stewart group (in collaboration with Prof Colin Farquharson, University of Edinburgh) propose the potential involvement of two enzymes, phospholipase A2 (PLA2) and ectonucleotide pyrophophatase/phosphodiesterase 6 (ENPP6), which may act together to generate inorganic phosphate from phosphatidylcholine in the MV membrane. Together they could produce phosphocholine, which in turn is a substrate for PHOSPHO1, an enzyme known to be essential for mineralization. The presented concept is backed up by various pieces of evidence; for example, both enzymes are expressed in mineralizing cells and it is known that phosphatidylcholine is broken down in MVs during mineralization. The paper, which will feature in a forthcoming issue, stemmed from a BSc(Hons) project that was researched by final year student, Darren Leong earlier this year.