Trace metals enzymes

Sierra EM, Rowles TK, Martin J, et al. 1989. Low level lead neurotoxicitv in a pregnant guinea pigs model Neuroglial enzyme activities and brain trace metal concentrations. Toxicology 59 81-96. 

Marine organisms concentrate metals in their tissues and skeletal materials. Many of these trace metals are classified as micronutrients because they are required, albeit in small amounts, for essential metabolic functions. Some are listed in Table 11.4, illustrating the role of metals in the enzyme systems involved in glycolysis, the tricarboxylic acid cycle, the electron-transport chain, photosynthesis, and protein metabolism. These micronutrients are also referred to as essential metals and, as discussed later, have the potential to be biolimiting. 

Table 11.4 Role of Trace Metals in Enzyme Systems.

In the experiments with galactose oxidase and dopamine -monooxygenase very low enzyme concentrations have often been used. The addition of an inert protein might help to approximate the natural conditions by providing a protection against surface denaturation and against radicals, and by regulating the trace metal concentrations. 

The chief use of molybdenum is in steels. The oxides and sulfides have some applications as catalysts. Molybdenum is the only element in the second and third transition series which appears to have a major role as a trace metal in enzymes. Several aspects of molybdenum chemistry have been widely studied in order to gain a better understanding of the biological relevance. Molybdenum is one of the few elements which currently has its own series of international conferences.1... 

Water accounts for over half the body mass (55%) of the average human. Of the remaining 45%, 19% is protein, 19% is lipid, less than 1% is carbohydrate, and 7% is inorganic material. Nutrients must contain the raw materials that go into the construction of the components of the human body. In addition, nutrients must supply the necessary chemical energy and enzyme cofactors (vitamins and trace metal elements) that are required for the maintenance and growth of the human body. The human body requires nutrients such as water, amino acids, fats, carbohydrates, and major minerals in large amounts. Vitamins and trace metal elements are required in smaller amounts. 

An enzyme cofactor can be either an inorganic ion (usually a metal cation) or a small organic molecule called a coenzyme. In fact, the requirement of many enzymes for metal-ion cofactors is the main reason behind our dietary need for trace minerals. Iron, zinc, copper, manganese, molybdenum, cobalt, nickel, and selenium are all essential trace elements that function as enzyme cofactors. A large number of different organic molecules also serve as coenzymes. Often, although not always, the coenzyme is a vitamin. Thiamine (vitamin Bj), for example, is a coenzyme required in the metabolism of carbohydrates. 

Jones, G. J., B. P. Palenik, and F. M. M. Morel. 1987. Trace metal reduction by phytoplankton The role of plasmalemma redox enzymes. Journal of Phycology 23 237-244. 

Artificial liver support systems aim at the extracorporeal removal of water soluble and protein-bound toxins (albumin being the preferential binding protein) associated with hepatic failure. Albumin contains reversible binding sites for substances such as fatty acids, hormones, enzymes, dyes, trace metals and drugs [26] and therefore helps elimination by kidneys of substances that are toxic in the unbound state. It should be noticed that the range of substances to be removed is broad and not completely identified. Clinical studies showed that the critical issue of the clinical syndrome in liver failure is the accumulation of toxins not cleared by the failing liver. Based on this hypothesis, the removal of lipophilic, albumin-bound substances, such as bilirubin, bile adds, metabolites of aromatic amino acids, medium-chain fatty acids, and cytokines, should be benefidal to the dinical course of a patient in liver failure. 

Identification of the varying biological functions, classification of the bioluminescent relationships between different organisms, elucidation of the detailed reaction pathway, and the possibility of convenient study of the effect of enzyme or substrate modification have all been prime motivations for the study of bioluminescence (McCapra, 1976 Henry and Michelson, 1978 Hastings and Wilson, 1976 Cormier et al., 1975). Interest in chemiluminescence has been stimulated by its remarkable sensitivity and often selectivity as an analytical tool. As a result, chemiluminescence has found extensive application in the detection of trace metals in solution (Montano and... 

ICP-MS was found to be compatible with LC for the trace metal speciation. The role of ICP-MS in trace element speciation studies at the FSL was described (Crews et al., 1987). The characteristics of LC-ICP-MS for the study of metalloprotein species were assessed and the chromatographic efficiency of ICP-MS was found to be similar to that obtained with a UV detector (Dean et al., 1987). Information about the chemical nature of trace elements from food can be obtained by first treating the foods in vitro with enzymes to broadly simulate the action of enzymes in the gastrointestinal tract (Crews et al., 1988). The soluble components can be separated by size exclusion chromatography (SEC) and an estimate of their molecular size obtained. By coupling SEC... 

Table 10.4. Some Enzymes and Redox Proteins Containing Trace Metal Cofactors...

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