ISOLATION AND CHARACTERIZATION OF THE CIRCULATING FORM OF HUMAN ENDOSTATIN

Recently, fragments of extracellular proteins, including endostatin, w ere defined as a novel group of angiogenesis inhibitors, In this study , human plasma equivalent hemofiltrate was used as a source for the pu rification of high molecular weight peptides (10-20 kDa), and the isol ation and identification of circulating human endostatin are described , The purification of this C-terminal fragment of collagen alpha 1(XVI II) was guided by MALDI-MS and the exact molecular mass determined by ESI-MS was found to be 18 494 Da, N-terminal sequencing revealed the i dentity of this putative angiogenesis inhibitor and its close relation to mouse endostatin, The cysteine residues 1-3 and 2-4 in the molecul e are linked by disulfide bridges, In vitro biological characterizatio n of the native protein demonstrated no antiproliferative activity on different endothelial cell types. These data indicate that human endos tatin, which is a putative angiogenesis inhibitor, is present in the c irculation. (C) 1997 Federation of European Biochemical Societies.