Zinc as a modulator of transglutaminase activity - Laboratory and pathophysiological aspects.

For a whole century, citrate has been used as an anticoagulant via chelation of calcium. Later, also EDTA was introduced as an anticoagulant. An often overlooked fact is that zinc is bound to citrate and EDTA with affinities much greater than that for calcium, imposing problems in biomedical research. , proteins of the S100 family are released from leukocytes and known to bind calcium. Some of them, e.g., calprotectin, also chelate zinc. Thus, at an inflamed site, the ratio between Ca and Zn is changed. This mechanism is of importance for the modulation of the activation of a fascinating family of post-translationally acting calcium-dependent thiol enzymes, the transglutaminases, which are inhibited by zinc. This presentation illustrates the complexity of studies with zinc. Moreover, it exemplifies the role of Zn in pathophysiological situations such as celiac disease and neurodegeneration.