Bioassay system

The 5-AMP-activated protein kinase (AMPK) is a key sensor of intracellular energy balance. AMPK is activated in response to an increase in the AMP/ATP ratio which can be caused by a number of factors such as muscle contraction, starvation, or hypoxia. AMPK is a heterotrimeric protein complex comprising of α - (63 kDa), β - (38 kDa) and γ - (38 kDa) subunits. For each subunit, isoforms have been identified ( α 1, α 2, β - 1, β - 2, γ 1, γ 2, γ 3) which theoretically allow the formation of 12 different proteins. The α -subunit contains a serine/threonine kinase domain and the regulatory subunits contain binding sites for AMP and ATP and for glycogen. AMPK is activated by phosphorylation on Thr-172 within the catalytic domain. AMP binding results in a 2 to 5-fold increase in AMPK activity compared to the basal level. Binding of AMP to the α -subunit causes allosteric activation of the kinase and induces a conformational change in the kinase domain that protects AMPK from dephosphoryla...

ACETYLCHOLINE   i s a neurotransmitter produced in acetylcholinergic neurons. It plays important roles in skeletal muscle movement, regulation of smooth and cardiac muscles, as well as in learning, memory and mood. BioAssay Systems method provides a simple, direct and high-throughput assay for measuring acetylcholine in biological samples. In this assay, acetylcholine is hydrolyzed by acetylcholinesterase to choline which is oxidized by choline oxidase to betaine and H 2 O 2 . The resulting H 2 O 2  reacts with a specific dye to form a pink colored product. The color intensity at 570nm or fluorescence intensity (530/585 nm) is directly proportional to the acetylcholine concentration in the sample.