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Title: AMP-activated protein kinase and cAMP-dependent protein kinase from mammary gland of lactating rat
Author: Milic, Mihajlo Radivoj
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1995
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Acetyl-CoA carboxylase (ACC) catalyses the first committed step in fatty acid synthesis and is regulated by reversible phosphorylation and inactivation. Although cAMP-dependent protein kinase (cAMP-PK) from bovine heart can phosphorylate and inactivate ACC in vitro, there is now much evidence to suggest that AMP-activated protein kinase (AMP-PK) is responsible for ACC phosphorylation and inactivation in vivo. AMP-PK from mammary gland was purified 3750 fold using a seven step purification, it has a native MW of 93 KDa and a possible heterodimer subunit structure with a larger catalytic subunit of 61-62 KDa. Mammary gland AMP-PK has a temperature optimum of 36°C, pH optimum at pH 7.0, Ka for 5’AMP of 1.4μM (assayed at 200μM ATP), Ki for FSBA of 170μM (assayed at 100μM 5’AMP and 200μM ATP). AMP-PK from mammary gland is allosterically activated by 5’AMP (2-3 fold at 100μM 5’AMP) and is reversibly phosphorylated and activated by a distinct "kinase-kinase". AMP-PK from mammary gland and liver of lactating rats have identical structural and kinetic properties indicating that they are not isozymic forms. Partially purified kinase kinase has proven not to be cAMP-PK from mammary gland but has many properties in common with a previously described but uncharacterised ACC-kinase from lactating rat mammary gland named ACC-kinase 2. AMP-PK appears to have a physiological role in the control of ACC activity during starvation and refeeding in the liver of virgin rats, and mammary gland of lactating rats. In both tissues changes in AMP-PK activity during starvation and refeeding closely correlate with reciprocal changes in the Vmax of ACC and with changes in plasma insulin concentration. The catalytic subunit of cAMP-PK (C-subunit) was purified from lactating rat mammary gland and compared with C-subunit from rat and bovine heart. Despite similar molecular weight, the mammary gland and heart C-subunits appear to be different isoenzymes based on their specific activities, their substrate specificity and Cleveland mapping on SDS-PAGE.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available