Aeschlimann D, Mosher D, Paulsson M
Department of Medicine, University of Wisconsin, Madison 53792-3228, USA.
Semin Thromb Hemost. 1996;22(5):437-43. doi: 10.1055/s-2007-999043.
While it is well established that factor XIII functions in crosslinking of the fibrin clot during blood coagulation and in wound healing, the physiological role of tissue transglutaminase is still unclear. Recent studies suggest that the expression of tissue transglutaminase correlates with (terminal) differentiation of cells and that the enzyme may play a role in extracellular matrix remodeling. In cartilage, tissue transglutaminase expression is restricted to hypertrophic chondrocytes and the enzyme is externalized at a distinct step in the chondrocyte maturation program. Upon activation by Ca2+, the transglutaminase modifies matrix constituents in a way that might predispose the matrix for the subsequent mineralization. Crosslinks of the structure gamma-glutamyl-epsilon-lysine are also abundant in bone matrix, but the transglutaminase expressed by osteoblasts and presumably involved in crosslinking of newly formed osteoid is likely to be distinct from both tissue transglutaminase and factor XIII. Matrix proteins thought to be crosslinked by transglutaminases in cartilage and bone matrix include glycoproteins such as osteonectin, osteopontin, fibronectin, fibrillin, and collagens II, III, V, and XI. Expression of the A subunit of factor XIII is restricted to megakaryocytes in the bone marrow cavity, and factor XIIIa is abundant in platelets that probably provide the major source for factor XIII in plasma.
虽然已经明确因子 XIII 在血液凝固过程中的纤维蛋白凝块交联以及伤口愈合中发挥作用，但组织转谷氨酰胺酶的生理作用仍不清楚。最近的研究表明，组织转谷氨酰胺酶的表达与细胞的（终末）分化相关，并且该酶可能在细胞外基质重塑中发挥作用。在软骨中，组织转谷氨酰胺酶的表达仅限于肥大软骨细胞，并且该酶在软骨细胞成熟程序的一个特定阶段被分泌到细胞外。在 Ca2+ 激活后，转谷氨酰胺酶以一种可能使基质易于随后矿化的方式修饰基质成分。γ-谷氨酰-ε-赖氨酸结构的交联在骨基质中也很丰富，但成骨细胞表达的、可能参与新形成类骨质交联的转谷氨酰胺酶可能与组织转谷氨酰胺酶和因子 XIII 都不同。在软骨和骨基质中被认为由转谷氨酰胺酶交联的基质蛋白包括糖蛋白，如骨连接蛋白、骨桥蛋白、纤连蛋白、原纤维蛋白以及胶原蛋白 II、III、V 和 XI。因子 XIII 的 A 亚基的表达仅限于骨髓腔中的巨核细胞，并且因子 XIIIa 在血小板中含量丰富，血小板可能是血浆中因子 XIII 的主要来源。
