Transaminase and glutamate dehydrogenase activity in Rangia cuneata / by Earl Hampton Crumpler, Jr.
| Author/creator | Crumpler, Earl Hampton author. |
| Other author | Ito, Takeru, degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 1980. |
| Description | 60 leaves : illustrations ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Energy metabolism in both aerobic and anaerobic organisms initially involves the reactions of glycolysis. However, many invertebrates appear to have developed an additional method of anaerobic ATP formation. Some examples included free living annelids (Schroff and Schottler, 1977), bivalves (Hochachka and Mustafa, 1972) as well as some bacteria (Dorn, et al., 1978). It appears that these organisms, which are capable of existing under sustained anoxic conditions, not only exhibited increased levels of enzymes associated with anaerobiosis but displayed a number of unique enzymatic pathways for anaerobic energy extraction (Hochachka and Somero, 1976). During anoxia these organisms relied upon the simultaneous mobilization of two energy sources, carbohydrates and amino acids. As a result, a multiplicity of end products were formed, such as (1) alanine, (2) succinate, (3) metabolic CO2, (4) propionate, (5) acetate and alanopine (Hochachka, 1980). Available evidence suggested that at least in some anaerobic invertebrates the metabolic fate of phosphoenolpyruvate (PEP) was quite different from that in other organisms. The metabolic pathway that appears to occur in these anaerobes is summarized below. As PEP is formed, it is channeled through a series of reactions resulting in the accumulation of two molecules of malate for every molecule of glucose that enters the pathway, instead of being converted to pyruvate by pyruvate kinase as this occurs in mammals. Mai ate may be converted to fumarate which, acting as a final electron acceptor, is reduced by NADH to succinate. Another malate molecule is a source of the NADH through the malic enzyme 2 reaction. The reduction of fumarate by the NADH (NADH fumarate reductase) appears to be mediated by the anaerobic electron transport system (NADH dehydrogenase. Coenzyme Q, etc.) associated with mitochondria, and to be coupled to the phosphorylation of ADP. The conversion of malate to pyruvate makes possible a glutamate-pyruvate transamination whereby a-ketoglutarate may be converted to succinyl CoA allowing for a potential substrate level phosphorylation (succinyl CoA synthetase) while alanine is a "switch" that controls the PEP branchpoint by inhibiting pyruvate kinase, thus making it possible to convert PEP into oxaloacetate by PEP carboxykinase. Therefore, the transaminase provides a means for the subsequent substrate level phosphorylation, another energy gain for the organism. In many organisms the a-ketoglutarate produced in the transamination is reconverted to glutamate by NADH linked glutamate dehydrogenase (GDH). Although the metabolic fate of PEP in anaerobic invertebrates just summarized was by no means established unequivocally, it is reasonable to hypothesize that the pathway also occurs in Rangia cuneata as well, unless proven otherwise. The work was concerned with examination of transaminase and GDH in the mantle tissue of a bivalve, Rangia cuneata, which is readily available in this area of the country. It was undertaken in order to help elucidate roles that these enzymes may play in the invertebrate anaerobic metabolism. |
| General note | Presented to the Faculty of the Department of Biology. |
| General note | Advisor: Takeru Ito |
| Dissertation note | M.S. East Carolina University |
| Bibliography note | Includes bibliographical references (leaves 58-60). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |