Kakegawa H, Tagami K, Ohba Y, Sumitani K, Kawata T, Katunuma N
Institute for Health Sciences, Tokushima Bunri University, Japan.
FEBS Lett. 1995 Aug 14;370(1-2):78-82. doi: 10.1016/0014-5793(95)00790-g.
Secretion of procathepsin L into the culture medium from a bone cell mixture was markedly enhanced by addition of parathyroid hormone (PTH), 1 alpha,25-(OH)2D3 or tumor necrosis factor alpha (TNF alpha). These stimulators of secretion of procathepsin L enhanced bone pit formation, which was inhibited by E-64, but not by CA-074, a specific inhibitor of cathepsin B. Procathepsin L may thus participate in the process of bone collagenolysis during bone resorption. Procathepsin L partially purified from rat long bones under cold conditions was rapidly converted to the mature form under acidic conditions at room temperature. This conversion was inhibited by E-64, suggesting that the procathepsin L secreted into lacunae is catalytically converted to the mature enzyme by cysteine proteinase(s).
