Introductory Mycology

first chapter, the author considers the "purpose" served by the second pyridine nucleotide coenzyme, TPN, to which he adds the thought that TPN arose in evolution to protect reducing power from the DPN-specific terminal oxidase systems that developed. Thus, the phosphogluconate and Emden-Myerhof pathways are looked at in terms of the pyridine nucleotidecoenzyme which each reduces rather than as alternate pathways to a common end. The transketolase-transaldolase route to pentose is considered here and the mechanism of these enzymes is discussed in detail in Chapter 3. The adaptive paths for xylose and arabinose degradation involving aldose-ketose conversion either by reduction-oxidation or by isomerase reaction in different microorganisms are thoroughly discussed with respect to the specific enzymes involved. As with man, the problem seems to be to get to D-xylulose-5-P. The pathway of heterolactic fermentation and role and mechanism of phosphoketolase are highlights of Chapter 2. Unfortunately for those who like to see the human aspects of scientific work, only occasionally, when in-progress work is discussed, is the reader made aware of the author as investigator. This may be proper journal protocol but it is regrettable that Horecker does not use this occasion to give his reader a more richly woven picture of the doings of one of our ablest enzymologists.