Publisher Summary This chapter describes the advances with an emphasis on the structures of the alcohol dehydrogenases and the relationship between structure and function Yeast and mammalian alcohol dehydrogenase differ in substrate specificity and rate of catalytic activity The classic yeast enzyme is more specific for acetaldehyde and ethanol, which is consistent with its recognized physiological Significance to participate in alcohol fermentation at the end of the glycolytic pathway Enzyme forms with other functions and properties also occur in yeast The mammalian enzymes have broad substrate specificity and, even with primary alcohols, the maximum activity is not observed with ethanol Alcohols including ethanol, produced in the intestinal tracts mainly by bacterial actions, are found in the portal vein One physiological function of liver alcohol dehydrogenase may be to metabolize these products Structural studies have established that mammalian alcohol dehydrogenases have a distant evolutionary link to both the yeast and bacterial enzymes Ingested alcohol is metabolized to acetaldehyde mainly by the action of liver alcohol dehydrogenase

3 Alcohol Dehydrogenases

INTRODUCTION 403 DEFINITION AND EXTENT OF REVIEW 404 HISTORICAL PERSPECTIVE 404 Discovery of Bound Auxins 404 THE NATURALLY OCCURRING BOUND AUXINS 406 Chemical Forms 406 The esters of Zea mays 406 Other naturally occurring conjugates ....... 407 Sites of Synthesis of Bound Auxins 409 Enzymatic Synthesis 409 Enzymatic Hydrolysis 411 Function of Naturally Occurring Auxin Conjugates 413 Storage of lAA 413 Protection of auxin against peroxidative attack ......... 413 Transport of indole auxins within the plant ....... 414 Hormonal homeostasis 41:; CONJUGATES FORMED FROM APPLIED AUXINS AND GROWTH REGULATORS 416 Chemical Forms 416 Enzymatic Synthesis 418 Enzymatic HydrolYSiS 418 Control of Conjugate Formation 419 Applications 419 CHEMICAL SYNTHESIS OF IAA CONJUGATES 420 CONCLUSIONS 421

Chemistry and Physiology of the Bound Auxins

The endosperm in seed development

This review focuses on the question of how protons are transported across membranes during bioenergetic processes. It has been found that proton transport through membranes is a central feature of several bioenergetic systems, such as bacteriorhodopsin, which pumps protons to higher free energies [115], and the ATP synthase, which consumes energetic protons [90]. In addition, it may be noted that proton transport has been implicated in transhydrogenase [28, 91], cytochrome oxidase, and the bcl redox loop in the mitochondrial respiratory chains [29, 90, 119]. ATP-driven proton pumps may be utilized in a variety of biological systems: evidence for them has been found in kidney [69] and liver [97] lysosomal vesicles, maize apical meristem plasmalemma [13], chromaffin granules [2], turtle bladder [1], Escherichia coli and Streptococcus lactis [68], and Neurospora crassa [36]. In addition, H + / K § antiport has been suggested to occur in alkaline tolerant strains of Bacillus firmus [38], in gastric parietal cells [102], and H § symport in E. coli [89]. While the question of proton transport mechanisms was stimulated by the delocalized chemiosmotic theory [72], it should be emphasized that the question is even more relevant for localized theories [120]. Indeed, for localized theories one requires proton transport for long distances along the membrane [49, 50, 86], not just proton transport across the membrane. It is also possible to imagine that even more extensive networks of proton pathways exist in the cell, perhaps utilizing the cytosol microstructure [5, 6]. Finally, proton transport may be a part of other bioenergetic mechanisms such as muscle action [75] or flagellar motion [34, 52]. It will not be our purpose to review the theories of Mitchell [72] and Williams [120]. These theories, which are very important, are phenomenological. They attempt to describe where various ions go and which enzymes and substrates are utilized, but they do not attempt to describe molecular mechanisms. One danger of purely phenomenological theories is that they may require processes for which no physical mechanisms exist. Our purpose will be to review theories of mechanisms for proton transport which can then be utilized within the framework of any phenomenological theories. Various kinds of active transmembrane proton transport can be envisaged (Fig. 1). One would involve a carrier molecule that would attach a proton and carry it across the membrane (Fig. 1 A). Another would involve a transmembrane protein

Hydrogen bonded chain mechanisms for proton conduction and proton pumping.

Growth and morphogenesis of the strawberry as related to auxin

Isolation of an auxin precursor and an auxin (indoleacetic acid) from maize

INCREASING ATTENTION is being paid to the extraction of auxin2 from the tissues of higher plants, particularly as regards reliability and yield in relation to various extraction procedures. A comparative study of eight different methods of auxin extraction from maize endosperm has been reported (Avery, Creighton and Shalucha, 1940), the methods dealt with being those formulated in the preceding five years by several different workers. From the standpoint of auxin yield per unit weight of tissue, two of the methods were outstanding: (1) successive extractions of the same batch of tissue with several different solvents (alcohol-chloroform-water), referred to as a multisolvent method; (2) extraction with water alone as a solvent. Our object at this time is to report further studies on these two methods for hormone extraction of maize endosperm. Yields have been increased to twenty times those previously reported from this laboratory. MATERIALS AND METHODS.-For reasons pointed out in the previous report, endosperms of maize (Zea mays L. var. Canada Flint3) are again used for auxin extraction studies. Skoog's (1937) "deseeded" Avena test method was used for auxin assays, the test schedule used already having appeared in publications of this laboratory. Agar block size (10 cmm.), units used, etc., are discussed in detail by Avery, Creighton and Shalucha (1941). The Avena test laboratory was maintained at 250C., 85-90 per cent relative humidity, and lighted only with phototropically inactive light. All yields4 are expressed on the basis of air-dry endosperm (ca. 9 per cent moisture) in terms of TDC/gm. The TDC unit has been used through1 Received for publication March 1, 1941. 2 In this paper, any compound which causes curvatures away from the applied agar block in the Avena test, is considered an "auxin." 3 Courtesy of Dr. Ralph Singleton, Connecticut Agricultural Experiment Station. 4 TDC=total degrees curvature in the "deseeded" Avena test method, and is calculated from the expression CX lbOX V w

Julius Berger

Papers

Isolation of an auxin precursor and an auxin (indoleacetic acid) from maize

The total extraction of free auxin and auxin precursor from plant tissue

Glutamic and isocitric acid dehydrogenases in the avena coleoptile and the effect of auxins on these enzymes

Auxin content of maize kernels during ontogeny, from plants of varying heterotic vigor

The mechanism of auxin action.