UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Regulatory processes in the central nervous system: A study of g-protein abundance and of soluble 5'-nucleotidase

Orford, Michael Robert; (1993) Regulatory processes in the central nervous system: A study of g-protein abundance and of soluble 5'-nucleotidase. Doctoral thesis (Ph.D), UCL (University College London). Green open access

[img] Text
Regulatory_processes_in_the_ce.pdf

Download (12MB)

Abstract

The abundance of G-protein α-subunits were measured by quantitative immunoblotting. Hypothyroidism increased the abundance of Gi1α, Gi2α and Goα in synaptosomal membranes from the cerebral cortex and striatum. In the other brain regions some but not all of the G-proteins were up-regulated. In hyperthyroidism the abundance of Gilα and Gi2α were halved in the cerebral cortex after only 3 days treatment with T3. Together these findings may in part contribute to physiological and behaviourial changes seen in thyroid abnormalities. Soluble 5’-nucleotidase (EC 3.1.3.5) was assayed in six regions of the rat brain. ATP inhibited the activity in a complex fashion suggesting the presence of at least two soluble enzymes; one being strongly inhibited and another being ATP activated. The proportions of these two activities varied between brain regions, and activity changes seen in hypothyroidism suggest that they may be independently regulated. The ATP-inhibitable enzyme was purified 1770 fold to apparent homogeneity. It appeared to be a 230kDa glycoprotein composed of 53kDa subunits. The purified enzyme showed activity towards most nucleoside 5’-monophosphates, but not towards their 2’-deoxyribose counterparts. AMP and UMP were preferred substrates and the enzyme had a Km for AMP of 15μM. ADP and ATP were potent inhibitors of enzyme activity, ATP inhibition being of the mixed type with a Ki of 67μM. This ATP inhibition could be reversed by magnesium ions indicating that free ATP was the inhibiting species. In the course of the purification, two enzyme populations were observed which exhibited different ATP and ADP inhibition characteristics. The differences appeared to be due to the presence of an unknown factor which appeared to be bound to a population of the enzyme hence altering its behaviour on ion exchange. Alone, the factor did not affect the enzyme, but did however greatly enhanced its ATP sensitivity. The factor could be stripped off the enzyme and reconstituted back in a saturable manner.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Regulatory processes in the central nervous system: A study of g-protein abundance and of soluble 5'-nucleotidase
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10097964
Downloads since deposit
14Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item