The importance of micronutrients in health and nutrition is undisputable, and among them, zinc is an essential element whose significance to health is increasingly appreciated and whose deficiency may play an important role in the appearance of diseases. Zinc is one of the most important trace elements in the organism, with three major biological roles, as catalyst, structural, and regulatory ion. Zinc-binding motifs are found in many proteins encoded by the human genome physiologically, and free zinc is mainly regulated at the single-cell level. Zinc has critical effect in homeostasis, in immune function, in oxidative stress, in apoptosis, and in aging, and significant disorders of great public health interest are associated with zinc deficiency. In many chronic diseases, including atherosclerosis, several malignancies, neurological disorders, autoimmune diseases, aging, age-related degenerative diseases, and Wilson's disease, the concurrent zinc deficiency may complicate the clinical features, affect adversely immunological status, increase oxidative stress, and lead to the generation of inflammatory cytokines. In these diseases, oxidative stress and chronic inflammation may play important causative roles. It is therefore important that status of zinc is assessed in any case and zinc deficiency is corrected, since the unique properties of zinc may have significant therapeutic benefits in these diseases. In the present paper, we review the zinc as a multipurpose trace element, its biological role in homeostasis, proliferation and apoptosis and its role in immunity and in chronic diseases, such as cancer, diabetes, depression, Wilson's disease, Alzheimer's disease, and other age-related diseases.

Background and Purpose Hydrogen sulfide (H2S) is a signalling molecule that belongs to the gasotransmitter family. Two major sources for endogenous enzymatic production of H2S are cystathionine β synthase (CBS) and cystathionine γ lyase (CSE). In the present study, we examined the selectivity of commonly used pharmacological inhibitors of H2S biosynthesis towards CSE and CBS.Experimental Approach To address this question, human CSE or CBS enzymes were expressed and purified from Escherichia coli as fusion proteins with GSH-S-transferase. After purification, the activity of the recombinant enzymes was tested using the methylene blue method.Key Results β-cyanoalanine (BCA) was more potent in inhibiting CSE than propargylglycine (PAG) (IC50 14 ± 0.2 μM vs. 40 ± 8 μM respectively). Similar to PAG, L-aminoethoxyvinylglycine (AVG) only inhibited CSE, but did so at much lower concentrations. On the other hand, aminooxyacetic acid (AOAA), a frequently used CBS inhibitor, was more potent in inhibiting CSE compared with BCA and PAG (IC50 1.1 ± 0.1 μM); the IC50 for AOAA for inhibiting CBS was 8.5 ± 0.7 μM. In line with our biochemical observations, relaxation to L-cysteine was blocked by AOAA in aortic rings that lacked CBS expression. Trifluoroalanine and hydroxylamine, two compounds that have also been used to block H2S biosynthesis, blocked the activity of CBS and CSE. Trifluoroalanine had a fourfold lower IC50 for CBS versus CSE, while hydroxylamine was 60-fold more selective against CSE.Conclusions and Implications In conclusion, although PAG, AVG and BCA exhibit selectivity in inhibiting CSE versus CBS, no selective pharmacological CBS inhibitor is currently available.

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ATP7A is a P-type ATPase involved in copper(I) homeostasis in humans. It possesses a long N-terminal tail protruding into the cytosol and containing six copper(I)-binding domains, which are individually folded and capable of binding one copper(I) ion. ATP7A receives copper from a soluble protein, the metallochaperone HAH1. The exact role and interplay of the six soluble domains is still quite unclear, as it has been extensively demonstrated that they are strongly redundant with respect to copper(I) transport in vivo. In the present work, a three-domain (fourth to sixth, MNK456) construct has been investigated in solution by NMR, in the absence and presence of copper(I). In addition, the interaction of MNK456 with copper(I)-HAH1 has been studied. It is proposed that the fourth domain is the preferential site for the initial interaction with the partner. A significant dependence of the overall domain dynamics on the metallation state and on the presence of HAH1 is observed. This dependence could constitute the molecular mechanism to trigger copper(I) translocation and/or ATP7A relocalization from the trans-Golgi network to the plasmatic membrane.Copper, an essential trace metal, is utilized as a cofactor in a variety of redox and hydrolytic proteins, which in eukaryotes are found in various cellular locations (1). However, copper can be potentially toxic in vivo, and thus its intracellular concentration is presumably strictly controlled (2-4). Disruption of copper homeostasis leads to illness, such as in Menkes or Wilson diseases (5). These latter diseases are caused by mutations in ATP7A and ATP7B, respectively, which translocate copper in the trans-Golgi network or across the plasma membrane (3, 4), depending on cellular conditions (6). Even though ATP7A and ATP7B contain six cytosolic copper(I)-binding domains, it appears that one domain (7, 8), or even no soluble domain if copper is abundant (9), is sufficient for copper translocation. In addition, only one of the two most C-terminal metal-binding domains is sufficient for correct protein relocalization (10), whereas both C-terminal metal-binding domains (i.e. the fifth and sixth domains) are needed to regulate copper affinity and protein phosphorylation rates (11). In humans, the function of HAH1 is to transfer copper(I) to the ATP7A and ATP7B proteins (12). This process has been investigated through a variety of low-resolution techniques, suggesting that there may be preferential interaction sites within the cytoplasmic tail (13,14). NMR data are available for the interaction of individual ATP7A soluble domains (2, 5, and 6) with HAH1, showing copper(I) transfer and a slow kinetics of interaction (15).The possible differentiation in vivo among the six domains, their possible reciprocal interaction(s), and the interactions with HAH1 and with copper(I) are all open matters of discussion. Here, these matters are addressed through the NMR investigation of a three-domain ATP7A construct, spanning domains 4 through 6 (MNK456 hereafter). 2This construct presents se...