Until recently, the major part of biochemical research has been concentrated on the degradative rather than on the synthetic reactions of living systems. This is mainly due to limitations imposed by technique. The introduction of isotopic tracers and the development of efficient fractionation techniques have made possible the investigation of the biosynthetic mechanism of many metabolites. During the last decade, due to the Coris and their coworkers, the mechanism of polysaccharide synthesis was largely worked out. Two years ago, Lynen and Mahler proposed independently a scheme for the biosynthesis of long-chain fatty acids. On the other hand, the problem of protein synthesis is still one of the major challenges to the biochemists. In the mechanisms just referred to for the biosynthesis of simpler metabolites, the specificity of the biochemical process is always explained by the specificity of the enzymes involved.But when the formation of a protein is considered, the problem cannot be solved by referring to the specificity of conventional protein enzymes, since the synthesis of these, in turn, has to be accounted for. Evidently, enzymes involved in protein biosynthesis must be of a different nature. Elucidation of the mechanism of protein synthesis will not only add to our knowledge about the production of cellular protein, but may also shed some light on many other important problems, e.g., heredity factors, cancer, virus growth and microbial adaptation. A prerequisite to the study of protein synthesis is to work out a simple system capable of net synthesis of a specific protein. Several approaches have been designed to demonstrate protein production in vivo and in vitro. The assets and limitations of each of these methods will be discussed in the next chapter. The approach adopted for the work reported in this dissertation is the net enzyme synthesis in vivo and in vitro. Enzymes offer a useful tool by virtue of being specific proteins which could be rapidly and accurately assayed. The larger portion of the work was carried out using the in vitro system since, in contrast with the in vivo system, it is simpler and permits better control of the experimental variables. The effect of several activators and inhibitors has been investigated with special emphasis on amino acid analogues"-- Introduction. / A Dissertation Submitted to the Graduate Council of Florida State University in partial fufillment of the requirements for the degree of Doctor of Philosophy. / Includes bibliographical references. / Earl Frieden, Professor Directing Dissertation; Karl Dittmer, Committee Member; Harold C. Beard, Committee Member; Russell Johnson, Committee Member; L.M. Beidler, Committee Member.

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

The primary objective of this study was to establish the nature and extent of the changes with age in sucrase, maltase and lactase activity in the small intestine of the laboratory Wistar rat, raised on a basal diet. The author was, in addition, interested in the possibility of these changes being brought about by the presence or absence of certain specific dietary factors. Analysis have shown marked changes in the activities of these three enzymes with advancing age in Wistar rats weaned at 21 days on to a basal diet. Lactase activity was found to remain at a high level from 18 to 20 days during which time a sharp and uniform drop in activity was indicated. The extent of this drop was found to be great, approximately 80 per cent of the pre-weaned level. In contrast sucrase activity of the small intestine in the pre-weaned rat was negligible and underwent a sharp increase in activity at the weaning age of 21 days. Maltase activity in the pre-weaned Wistar rat was appreciable and was found to increase significantly at weaning. Early weaning at 15 days brought about an earlier decline in lactase activity and a corresponding early rise in sucrase and maltase activities. When early weaning was immediately followed by the feeding of condensed milk no apparent maintenance of lactase activity was noted. Similarily when older rats, 28 days of age, were fed condensed milk no increase in lactase activity was apparent. Neither the condensed milk nor basal diets induced apparent differences on the effect of early weaning on sucrase and maltase activity. Apparent maintenance of lactase activity above those levels demonstrated in rats weaned at 21 days on to a basal diet was accomplished by fostering 16 day old rats on dams which had littered from four to five days prior to this transfer and which were assumed to be lactating at a somewhat greater rate than had the original mothers. It was noted however that this fostering process had no apparent influence on the extent of the changes in sucrase and maltase activities. The feeding of purified sugar diets containing two different levels of each of the three sugars, sucrose, maltose and lactose, had little effect on any of the three carbohydrases studied. Growth rates of the rats on these purified diets showed marked differences. The author suggests that the maintenance of lactase activity might be associated with the presence of an inductive component present in the milk of the freshly lactating dam, a component not necessarily present in the milk of the later period of lactation, and not necessarily a component of processed cow's milk. The absence of an adaptive lactase response to the feeding of lactose in this study and those of other workers suggest that lactose itself is unlikely this inducer. No adaptive response to substrates could be demonstrated for either sucrase or maltase. / Land and Food Systems, Faculty of / Graduate

A study was undertaken of effects of 2,4-D on enzyme action in plants (in vivo) and on enzyme kinetics (in vitoo). Bean plants were treated by spraying with a water solution of NH₄2,4-D. Harvests were made at intervals and enzyme activity was estimated using standard procedures. Extracts were prepared for estimation by grinding the plant material in water using a Waring Blendor. The enzymes amylase, peroxidase, catalase, phosphatase and phosphorylase were studied. Amylase activity in stem and leaf increased at first then decreased. Peroxidase in stem, decreased, then increased very greatly. In leaf, peroxidase increased steadily, Phosphorylase increased in stem and leaf for most of the period of six day over which determinations were made. Phosphatase increased in leaf, showed little change in stem. Catalase in leaf decreased. In vitro studies indicate slight activation of catalase at low concentrations and up to 100ppm. Stem phosphatase shows inhibition at concentrations of 500 and 1000 ppm. Effect on leaf phosphatase is variable. Stem phosphorylase is activated at concentrations of 1 to 1000 ppm. Modifications of metabolism resulting from enzyme changes are discussed. A theory of action of 2,4-D is put forth, which suggests that the chemical acts by inhibition or by activation of enzyme systems and that the plant responds by accelerated or depressed production of the enzyme in question, in accord with Hinshelwood’s theory of drug adaptation by bacteria. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

Thesis (Ph.D.)--Columbia University, [1932?]. / Description based on print version record. Includes bibliographical references (p. 33-34).

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 74-85) Also available in print.

Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. George Pierce, committee chair; E. Gilbert, Sidney Crow, committee members. Description based on contents viewed July 17, 2009. Includes bibliographical references (p. 124-135).

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Hung-wen Liu. Vita. Includes bibliographical references.

Thesis (Ph. D. (Biochemistry, Microbiology & Biotechnology))--Rhodes University, 2005.