Action of plant proteinase inhibitors on enzymes of physiopathological importance

Obtained from leguminous seeds, various plant proteins inhibit animal proteinases, including human, and can be considered for the development of compounds with biological activity. Inhibitors from the Bowman-Birk and plant Kunitz-type family have been characterized by proteinase specificity, primary structure and reactive site. Our group mostly studies the genus Bauhinia, mainly the species bauhinioides, rufa, ungulata and variegata. In some species, more than one inhibitor was characterized, exhibiting different properties. Although proteins from this group share high structural similarity, they present differences in proteinase inhibition, explored in studies using diverse biological models.

Obtidas de sementes leguminosas, várias proteínas inibem proteinases de origem animal, incluindo humanas, e podem ser consideradas para o desenvolvimento de compostos com atividade biológica. Inibidores da família Bowman-Birk e da família Kunitz vegetal tem sido caracterizados em relação a especificidade para proteinase, estrutura primária e sitio reativo. O nosso grupo majoritariamente vem estudando o gênero Bauhinia, principalmente as espécies bauhinioides, rufa, ungulatae variegata. Em algumas espécies, mais de um inibidor com propriedades diferentes foi caracterizado. Embora tais proteínas apresentem alta similaridade estrutural, diferem quanto à inibição de proteinases, e foram exploradas em estudos utilizando diversos modelos biológicos.

Glycosaminoglycans affect the interaction of human plasma kallikrein with plasminogen, factor XII and inhibitors

Human plasma kallikrein, a serine proteinase, plays a key role in intrinsic blood clotting, in the kallikrein-kinin system, and in fibrinolysis. The proteolytic enzymes involved in these processes are usually controlled by specific inhibitors and may be influenced by several factors including glycosaminoglycans, as recently demonstrated by our group. The aim of the present study was to investigate the effect of glycosaminoglycans (30 to 250 æg/ml) on kallikrein activity on plasminogen and factor XII and on the inhibition of kallikrein by the plasma proteins C1-inhibitor and antithrombin. Almost all available glycosaminoglycans (heparin, heparan sulfate, bovine and tuna dermatan sulfate, chondroitin 4- and 6-sulfates) reduced (1.2 to 3.0 times) the catalytic efficiency of kallikrein (in a nanomolar range) on the hydrolysis of plasminogen (0.3 to 1.8 æM) and increased (1.9 to 7.7 times) the enzyme efficiency in factor XII (0.1 to 10 æM) activation. On the other hand, heparin, heparan sulfate, and bovine and tuna dermatan sulfate improved (1.2 to 3.4 times) kallikrein inhibition by antithrombin (1.4 æM), while chondroitin 4- and 6-sulfates reduced it (1.3 times). Heparin and heparan sulfate increased (1.4 times) the enzyme inhibition by the C1-inhibitor (150 nM)