The research outlined in this dissertation represents a study towards the examination of the presence of mitochondrial arginine kinase (AK) activity in horseshoe crab (Limulus polyphemus) hearts and its possible physiological significance. The existence of such a mitochondrial bound AK was hinted at by the residual enzymatic activity in the mitochondrial pellet and the ability of arginine to stimulate state 3 respiration in the presence of ATP. The presence of a mitochondrial bound AK (AKm) in L. polyphemus hearts was confirmed by sucrose-density centrifugation and solubilization experiments. Between 1.5 and 2% of total cytoplasmic AK activity appeared to be associated with the mitochondria. Cellulose acetate electrophoresis revealed the existence of two populations of AKm--a 'fast' electrophoretic form (AKmf), migrating identically to cytoplasmic AK (AKc), and a 'slow' electrophoretic form (AKms). Both forms were present in a 1:1 ratio. The 'fast' form was easily extractable while AKms showed hydrophobic characteristics, only extractable with detergents. SDS-PAGE electrophoresis of these isoenzymes following purification showed the molecular weight subunit of both AKc and AKmf to be virtually the same (39-40 kD), but that of AKms being slightly higher (43.5 kD). The peptide maps of AKc and AKmf were identical, whereas that of AKms displayed some unique peptide fragments. AKmf is therefore thought to be a similar protein as AKc while AKmf may contain, however, an additional hydrophobic sequence for insertion and anchoring into the inner membrane of the mitochondrion. / Kinetic and thermodynamic experiments in the presence and absence of oxidative phosphorylation (OP) showed no difference in the kinetic parameters or movement of the mass action ratio, respectively. These results thus do not suggest effective functional coupling between OP (e.g. the adenosine nucleotide translocator) and the AKm reaction. These experiments exclude the possibility that there is preferential access of the AKm enzyme(s) for the product of respiration (ATP). A study comparing the efficacy of bound mitochondrial AK versus a soluble source of ADP showed that mitochondrial associated AK might be advantageous by minimizing the diffusion of ADP. / Source: Dissertation Abstracts International, Volume: 51-03, Section: B, page: 1077. / Major Professor: William Ross Ellington. / Thesis (Ph.D.)--The Florida State University, 1990.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78212 |
| Contributors | Doumen, Chris., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 164 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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