Intracellular metal concentrations, regulation

Metallothioneins (MTs) are a superfamily of low-molecular-weight (<7000-dalton) intracellular metal-binding proteins, which, in many species, play a critical role in (a) the detoxification of nonessential metals such as Cd2+ and Hg2+ and (b) the regulation of intracellular concentrations of essential metals such as Zn2+ and Cu+. In 1957, Kagi and Vallee first purified and characterized MT as a cadmium-binding protein in equine kidney. 

ADP (Adenosine diphosphate) 536 in adenylate system 302 - 304 complexes with metal ions 296 dissociation as acid 288 intracellular concentration 304 P-31 NMR spectrum 642 pka value of 293 in regulation 535 ADP-ribose (ADPR) 315, 778, 780 ADP-ribosylation 545, 778 ADP-ribosylation factors (ARFs) 559 Adrenaline (epinephrine) 534, 542, 553, 553s in adrenergic receptor 535 a-Adrenergic receptors 553, 558, 563 p-Adrenergic receptors 553, 554 in asthma 553 in heart failure 553 receptor kinase 553 structure (proposed) 534, 555 topology 555... 

All enzymes exhibit various features that could conceivably be elements in the regulation of their activity in cells. All have a characteristic pH optimum which makes it possible for their catalytic rates to be altered by changes in intracellular pH (e.g. in ribulose diphosphate carboxylase(l7>). The activities also depend on the concentration of substrates, which may vary according to intracellular conditions. Moreover, many require metal ions or vitamins, and the activity of enzymes may be a function of the concentrations in which such materials are present (e.g. the effect of iron limitation on the citric acid fermentation of Aspergillus niger ). However, over and above these factors, some enzymes have other properties that... 

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