title: Planetary change and biochemical adaptation: molecular evolution of corrinoid and heme biosyntheses.
abstract: This review examines the evidence suggesting that the anaerobic biosynthesis of cobalamin (vitamin B12) evolved during early stages of cell evolution and was quickly recruited in the pathway leading to deoxyribonucleotides, the building blocks of DNA genomes. Biochemical  evolution preceding the synthesis of the heme group and related molecules is discussed within the framework of geological evolution in which the appearance and accumulation of an oxygen-rich atmosphere stands as one of the major events in the evolution of the planet and the biosphere.
authors.affiliation: Facultad de Ciencias, UNAM, Mexico. alar@ciencias.unam.mx
authors.forename: Antonio
authors.initials: A
authors.lastname: Lazcano
mesh_terms: D000818:Animals; D045728:Corrinoids / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D019419:Evolution, Planetary; D006418:Heme / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D014805:Vitamin B 12 / Q000235:genetics / Q000378:metabolism
chemical_list: D045728:Corrinoids; D006418:Heme; D004247:DNA; D014805:Vitamin B 12