Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 96-123).

Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Five hexose kinases, two fructokinases and three hexokinases, were identified in sugarcane culm. Fructokinase, a fructose specific hexose phosphorylating enzyme, was further investigated. Two isoforms, FRK1 and FRK2, were found. The isoforms were purified to homogeneity and antibodies raised against each. Both FRK1 and FRK2 have pH optima of 8.0 and both are homodimers of 69 kDa, consisting of subunits of 33 kDa. FRK2 was subject to substrate inhibition by fructose concentrations exceeding 0.1 mM while FRK1 was not inhibited by 1.0 mM fructose. Sugarcane FRK2 is more sensitive to substrate inhibition than FRK2 from other plants. The reaction catalysed by FRK1 is ATP-specific. The FRK2 reaction can utilise a variety of nucleotide triphosphates and no substrate inhibition is apparent when assayed with UTP instead of ATP. We proposed the existence of two nucleotide triphosphate binding sites on the enzymes. One of the sites is an ATP-specific regulatory site while the other is a catalytic site with wide substrate specificity. Additionally two fructose-binding sites are proposed. One is a catalytic site and the other a allosteric regulatory site. Binding of fructose to the allosteric site is only possible if ATP is present in the regulatory ATP-binding site. Such a configuration could explain the kinetic properties of FRK2. Both fructokinase protein expression and total fructokinase activity decreased during development. Consequently the decrease in activity is the result of decreased expression and not inactivation of existing protein. The ratio of FRK2 to FRK1 activity is dependent on the developmental stage of the tissue. FRK1 appears to be the isoform that is preferentially expressed in mature tissue. Previous measurements of fructokinase activity in crude extracts have been inaccurate as a result of the divergent kinetic properties of the isoforms. Based on the findings in this project a novel method is proposed whereby both the activity of each isoform and total fructokinase activity can be accurately calculated using a mathematical equation. / AFRIKAANSE OPSOMMING: Vyf heksokinases, twee fruktokinases en drie heksokinases, is in suikerrietstingel ge'ldentifiseer. Fruktokinase, In fruktose-spesifieke heksose fosforileringsensiem, is verder ondersoek. Twee isovorme, FRK1 en FRK2, is gevind. Die isovorme is gesuiwer tot homogeniteit en teenliggarne is teen beide vervaardig. FRK1 en FRK2 het albei In pH optimum van 8.0 en beide is homodimere van 69 kDa, bestaande uit subeenhede van 33 kDa. FRK2 is baie gevoelig vir substraatremming deur fruktose, terwyl FRK1 nie gerem word deur konsentrasies selfs so hoog as 1.0 mM fruktose nie. Suikerriet FRK2 is meer sensitief vir substraatremming as FRK2 van ander plante. Die reaksie wat deur FRK1 gekataliseer word, is ATP-spesifiek. Die FRK2-reaksie kan In verskeidenheid nukleotiedtrifosfate benut en geen substraatremming kom voor wanneer die reaksie gemeet word met UTP in plaas van ATP nie. Gebaseer op die bevindinge word "n model voorgestel waar twee nukleotiedtrifosfaatbindingsetels op die ensieme voorkom. Een van die setels is In ATP-spesifieke regulatoriese setel, terwyl die ander In katalitiese setel met bree substraatspesifisiteit is. Verder postuleer ons twee fruktose-bindingsetels. Een van die setels is katalities en die ander een is 'n allosteriese regulatoriese setel. Binding van fruktose aan die allosteriese setel kan net plaasvind as ATP gebind is in die ATP-regulatoriese setel. So 'n konformasie kan die kinetiese eienskappe van FRK2 verduidelik. Die uitdrukking van fruktokinase-proteren en die totale fruktokinase-aktiwiteit neem beide af gedurende ontwikkeling. Gevolglik is die afname in aktiwiteit die gevolg van verminderde protelenuitdrukkinq en nie inaktivering van bestaande proteten nie. Die verhouding van FRK1- tot FRK2-aktiwiteit is afhanklik van die ontwikkelingstadium van die weefsel. Dit wil voorkom of FRK1 die isovorm is wat by voorkeur in volwasse weefsel uitgedruk word. Vorige bepalings van fruktokinase-aktiwiteit in ru-ekstrakte was onakkuraat as gevolg van die uiteenlopende kinetiese eienskappe van die isovorme. Gebaseer op die bevindinge van hierdie projek stel ons In oorspronklike metode voor waarvolgens beide die aktiwiteit van elke isovorm en totale fruktokinase-aktiwiteit akkuraat bereken kan word met behulp van 'n wiskundige formule.

published_or_final_version / Medicine / Master / Master of Philosophy

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13062号 / 論医博第2120号 / 新制||医||1018(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 長船 健二, 教授 川口 義弥, 教授 松田 道行 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 127-168).

Thesis (Ph.D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 127-168) Also available in print.

published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

Thesis (MSc (Biomedical Technology))--Cape Peninsula University of Technology, 2017. / Background: Telomeres are DNA-proteins situated at the ends of linear chromosomes, responsible for genome stabilization. A link has been previously described between leucocyte telomere length (LTL) and age-related inflammatory disorders such as atherosclerosis, rheumatoid arthritis and cancer. Since diabetes mellitus has been described as a chronic inflammatory condition, it has been hypothesized that there is significant LTL shortening in individuals with dysglycaemia. Aim: To investigate leucocyte telomere length in patients with pre-diabetes, newly diagnosed, known diabetics on treatment and to compare the results to normoglycaemic individuals. Methods: A total of 205 eligible subjects (78% women) median age 56 years, from the Bellville-South community were followed-up between 2008 and 2011. Baseline and follow-up data collections included glucose tolerance status, anthropometric, blood pressure, lipids, insulin, γ-glutamyl transferase, cotinine, and HbA1c. In all participants, telomere length was measured using the absolute telomere q-PCR method performed on a Bio-Rad MiniOpticon Detector. Results: Although there was a change in individuals’ glycaemic status over the 3 years, no significant differences were observed in LTL across glycaemic status: (Baseline p = 0.7618, 3 Year Follow-up p = 0.2204). However, in a multiple regression model, adjusted for age and gender, LTL was negatively associated with age and GGT, and positively associated with high density lipoproteins (HDL) (all p < 0.05). Discussion and conclusion: This research study was the first longitudinal study of LTL in Africans. We show that LTL shortening is not evident within three years, nor is it associated with glycaemia. Our findings also corroborate previous notions associating LTL with age. The lack of association between LTL and glycaemia has been previously reported, however further studies are required using larger sample and broader BMI spread.

Thesis (M.S.)--Brigham Young University. Dept. of Physiology and Developmental Biology, 2007. / Includes bibliographical references (p. 46-54).