The biochemistry of cobalt

Lin, Y. Nageswara Rao, B.D. Structural characterization of adenine nucleotides bound to Escherichia coli adenylate kinase. 2. P and C Relaxation measurements in the presence of cobalt(II) and manganese(ll). Biochemistry, 39, 3647-3655 (2000)... 

Coordination complexes, particularly chelates, play fundamental roles in the biochemistry of both plants and animals. Trace amounts of at least nine transition elements are essential to life—vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, and molybdenum. 

In order to accommodate new material, several changes have been made. The first four chapters have been modified so as to eliminate the more elementary aspects of atomic structure and give more coverage of symmetry and molecular structure. Various rearrangements of chapters and of material within sections have been made. One new chapter, on selected aspects of homogeneous catalysis by transition metal organometallic compounds has been added while some information on the biochemistry of iron, copper, cobalt, zinc and molybdenum is now provided. 

The importance of coordination in the biochemistry of essential metallic elements may be illustrated by numerous examples of metal complexes of which the following are representative the iron complex hemoglobin and numerous enzymes containing the heme and related structures such as catalases, peroxidases and cytochromes and the iron-containing proteins ferritin, transferrin, and hemosiderin the zinc complexes zinc-insulin, carbonic anhydrase and the carboxypeptidases the cobalt complex vitamin B12 the copper complex, ceruloplasmin the molybdenum-containing enzymes, xanthine oxidase, and nitrate reductase DNA-metal ion complexes. 

In contrast to iron and copper, which dominate the scene of transition metal biochemistry and are components of a variety of metalloproteins, cobalt occupies a relatively modest niche in biology. A biological function of cobalt can only be said to have been established at the molecular level in a few cases involving coninoid coenzymes (7). 

Most of the literature on cobalt(II) in biochemistry concerns its effects in various metal-activated enzyme systems (3). Many of the typical Mg2+-activated enzymes can work with Co2+, though usually at a low rate. In some other systems, where Mnz+ commonly is the best coenzyme, Co2+ gives high activities while other cations are less effective or inhibitory. A few enzymes, notably some metal-activated peptidases, are most efficient with Co2+, but other metal ions are also functional. It is not believed, however, that Co2+ is an important enzyme activator in vivo (4). 

Taylor, P. W., Feeney, J., and Burgen, A. S. V. Investigation of the mechanism of ligand binding with cobalt (II) human carbonic anhydrase by lH and 19F nuclear magnetic resonance spectroscopy. Biochemistry JO, 3866-3875 (1971). 

Licht, S. S., Booker, S., and Stubbe, J., 1999a, Studies on the catalysis of carbon-cobalt bond homolysis by ribonucleoside triphosphate reductase evidence for concerted carbon-cobalt bond homolysis and thiyl radical formation. Biochemistry 38 12219 1233. 

Fig. 2.20 Formal fitness landscape of various biocatalytic and inactive (i.e., the latter being located outside the window of essentiality ) metal ions for the carboxypeptidase A (Vallee and Williams 1968). The enzyme reconstituted by cobalt (treatment with EDTA, then addition of Co +) is considerably more active than the native Zn version , while Cd (and other ions) afford poorly to non-active metalloproteins in this case. (Relative) catalytic turnover rates are from Vallee and Williams 1968, x and c values this work and previous publications by this author. Here, sufficient abundance of the corresponding ions is taken for granted owing to in-vitro addition to apoprotein, so c k is not hmited by c, but merely represents the catalytic features pertinent to k, obtained from either biochemistry (several metal ions being present, e.g. in phosphatases) or experiments with reconstituted apoproteins...

Perhaps the most important area of biochemistry in which ESR is used is the study of metalloproteins. Transition metals in certain oxidation and spin states have unpaired electrons, are paramagnetic, and in many cases are amenable to ESR spectroscopy. The most commonly found transition metals in biological systems are iron, copper, molybdenum, cobalt, and manganese. The remainder, including metals such as vanadium and... 

Volumes have been published about the biochemistry and pharmacology of elements such as iron, cobalt, zinc, etc. (see, for example, the articles by P.M. May and D.R. Williams in Iron Metabolism edited by... 

Unravelling the biosynthetic steps leading from uro gen 111 to cobalamin, the finished cobalt corrin at the heart of vitamin B,2, is a story that has been likened to the climbing of Mt. Everest. It will one day be seen as the solution to one of chemistry s and biochemistry s greatest puzzles. Only the outline of the "ascent" will be given here. 

In biological systems, vitamin Bjj consists of an apoenzyme-coenzyme complex. The coenzyme is a cobalt complex that can be isolated by denaturation of the peptide. The chemistry and biochemistry of coenzyme are the subject of a several compilations and reviews. ... 

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