Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Zinc enzymology is, compared to some other current areas of metallobiochemistry, a maturing field, but in addition to further developments of structure-function relationships it has also provided a number of surprising new results and ideas in the last few years. In fact, the number of studies makes it impossible to provide a comprehensive review of the recent literature on zinc enzymology here, and the authors therefore focus on those zinc enzymes for which structure-function relationships are possible on the basis of structural and biochemical data. This means that, with a few exceptions, only zinc enzymes for which NMR or crystal structures are available are included here. Another seemingly simple, yet experimentally sometimes complex issue concerns the choice of which metalloenzyme is a zinc enzyme. Since there is in principle no difference in chemical catalysis by low-affinity compared to high-affinity metal sites, some of these enzymes are also included in this article, especially if they are or have been discussed as zinc enzymes, or are active with zinc. 552 refs.

Recent Advances in Zinc Enzymology

Spin—spin coupling and the conformational states of peptide systems

The molecular structure of rabbit muscle pyruvate kinase, crystallized as a complex with Mn2+, K+, and pyruvate, has been solved to 2.9-A resolution. Crystals employed in the investigation belonged to the space group P1 and had unit cell dimensions a = 83.6 A, b = 109.9 A, c = 146.8 A, alpha = 94.9 degrees, beta = 93.6 degrees, and gamma = 112.3 degrees. There were two tetramers in the asymmetric unit. The structure was solved by molecular replacement, using as the search model the coordinates of the tetramer of pyruvate kinase from cat muscle [Muirhead, H., Claydon, D. A., Barford, D., Lorimer, C. G., Fothergill-Gilmore, L. A., Schiltz, E., & Schmitt, W. (1986) EMBO J.5, 475-481]. The amino acid sequence derived from the cDNA coding for the enzyme from rabbit muscle was fit to the electron density. The rabbit and cat muscle enzymes have approximately 94% sequence identity, and the folding patterns are expected to be nearly identical. There are, however, three regions where the topological models of the cat and rabbit pyruvate kinases differ. Mn2+ coordinates to the protein through the carboxylate side chains of Glu 271 and Asp 295. These two residues are strictly conserved in all known pyruvate kinases. In addition, the density for Mn2+ is connected to that of pyruvate, consistent with chelation through a carboxylate oxygen and the carbonyl oxygen of the substrate. The epsilon-NH2 of Lys 269 and the OH of Thr 327 lie on either side of the methyl group of bound pyruvate. Spherical electron density, assigned to K+, is located within a well-defined pocket of four oxygen ligands contributed by the carbonyl oxygen of Thr 113, O gamma of Ser 76, O delta 1 of Asn 74, and O delta 2 of Asp 112. The interaction of Asp 112 with the side chains of Lys 269 and Arg 72 may mediate, indirectly, monovalent cation effects on activity.

F.J. Kayne

Papers

Thallium-205 Nuclear Magnetic Resonance Study of Pyruvate Kinase and Its Substrates EVIDENCE FOR A SUBSTRATE-INDUCED CONFORMATIONAL CHANGE