Cobalt chelatase Cobalt chelatase Cobalt chelatase () is an enzyme that catalyzes the chemical reaction The 4 substrates of this enzyme are ATP, hydrogenobyrinic acid a,c-diamide, Co, and HO, whereas its 4 products are ADP, phosphate, cob(II)yrinic acid a,c-diamide, and H. The aerobic cobalt chelatase (aerobic cobalamin biosynthesis pathway) consists of three subunits, CobT, CobN () and CobS (). Cobalamin (vitamin B12) can be complexed with metal via the ATP-dependent reactions (aerobic pathway) (e.g., in "Pseudomonas denitrificans") or via ATP-independent reactions (anaerobic pathway) (e.g., in "Salmonella typhimurium"). The corresponding cobalt chelatases are not homologous. However, aerobic cobalt chelatase subunits CobN and CobS
Chemical element which includes a discussion of the composition of inorganic and organic bodies and is a speculative treatise on chemistry. Plato believed the elements introduced a century earlier by Empedocles were composed of small polyhedral forms: tetrahedron (fire), octahedron (air), icosahedron (water), and cube (earth). Aristotle, c. 350 BCE, also used the term "stoicheia" and added a fifth element called aether, which formed the heavens. Aristotle defined an element as: In 1661, Robert Boyle proposed his theory of corpuscularism which favoured the analysis of matter as constituted by irreducible units of matter (atoms) and, choosing to side with neither Aristotle's view