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Title: Carnosine and related peptides in mammalian tissues
Author: Ng, W. L.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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Carnosine, homocarnosine and anserine were found to be present in rat quadriceps, gastrocnemius, and pectoral muscles, and in spinal cord and brain. These dipeptides could not be detected in heart, lung, kidney, liver or testes. A method for the determination of carnosine and related compounds, using reverse phase HPLC, has been developed. A novel colorimetric method, based on the formation of a coloured complex with Cobalt (II), was also developed for the determination of carnosine. The distribution of carnosine synthetase and homocarnosine synthetase in rat spinal cord, brain or skeletal muscles was studied. Carnosine synthetase was also shown to be responsible for anserine synthesis. On gel-filtration, carnosine synthetase separates into two active fractions (Mr 250,000 and 120,000). Homocarnosine synthetase has a Mr of 115,000. A requirement by carnosine synthetase for NAD+ and glucose was confirmed. Pyridoxal-5-monophosphate effectively replaced the requirement for glucose; a hypothesis is presented to explain this. Ca2+ ions were shown to activate carnosine synthetase but not homocarnosine synthetase. Significant effects on carnosine and homocarnosine synthetase from rat brain and gastrocnemius were produced by 5'-AMP, 5'-cAMP, 5'-GMP and 3',5'-cGMP. Carnosine synthetase activity, both from rat brain and from gastrocnemius, was inhibited by α-alanine which was shown to be an alternative substrate to β-alanine resulting in formation of L-α-alanyl-L-histidine. Carnosinase and homocarnosinase were partially purified from brain and from gastrocnemius. Carnosinase has a M_r of 120,000 and 50,000 and was activated by dithioerythritol. Homocarnosinase has a M_r of 54,000. Carnosinase was insensitive to thiol compounds and a range of metal ions. Homocarnosinase was activated by Co^2+ ions and was inhibited by thiol compounds. The K_m for carnosinase and homocarnosinase was found to be 4.0 mM and 1.0 mM, respectively. Carnosine, homocarnosine and anserine were shown to have no effect on hexokinase, phosphofructokinase, α-oxoglutarate, NAD+-isocitrate dehydrogenase and pyruvic dehydrogenase.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available