Biosyntheses

The present work emphasises the importance of microbial physiology, biochemistry, genetics and evolu­ tion in the study of biosynthesis. It takes into account the considerable advances made in the field in the last twenty years by the introduction of gene cloning and sequencing and by the exponential development of physical methods such as X-ray crystallography of proteins.After dealing with the kinetics of bacterial growth and the most recent developments in the mechanisms of cellular permeability, a chapter treats the phenomenon of allostery, indispensable for the understanding of many phenomena described in the rest of the book.Enzyme induction is then described from the phenomenological, genetic, and mechanistic points of view. Logically, the study of transcription follows, as well as that of repression in anabolic systems. The facts uncovered lead to the generalization of the concepts of negative and positive regulation.A study of the genetic code, of the transfer RNAs, and of the cognate aminoacyl-tRNA synthetases is an obligatory introduction to the phenomenon of attenuation.Then, eighteen chapters deal with the methodology of the elucidation of biosynthetic pathways and with these actual pathways including nitrogen fixation, polysaccharide and lipid biosyntheses, biosynthesis of amino acids, nucleotides and deoxynucleotides, water-soluble vitamins and coenzymes, metabolites deri­ ved from mevalonic acid (ubiquinones and menaquinones, carotenoids and sterols), tetrapyrrole com­ pounds (heme, chlorophyll and phycobilin chromophores) and, finally, cobalamins.