English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

1. Pyruvate kinase purified from the hepatopancrease of Carcinus maenas exhibited sigmoidal saturation kinetics with respect to the substrate phosphoenolpyruvate in the absence of the allosteric activator fructose 1,6-bisphosphate, but normal hyperbolic saturation was seen in the presence of this activator. The activation appears to be the result of a decrease in the s0.5 (phosphoenolpyruvate) and not to a change in Vmax. 2. In the presence of ADP and ATP at a constant nucleotide-pool size the results indicate that phosphoenolpyruvate co-operativity is lost on increasing the [ATP]/[ADP] ratio. 3. Paralleling this change is the observation that the fructose 1,6-bisphosphate activation became less at the [ATP]/[ATP] ratio was increased. This  was due to the enzyme exhibiting a near-maximal activity in the absence of activator. 4. L-Alanine inhibited the enzyme, but homotropic co-operative interactions were only seen with a cruder (1g supernatant) enzyme preparation. The inhibition by alanine could be overcome by increasing the concentration of either phosphoenolpyruvate or fructose 1,6-bisphosphate, although increasing the L-alanine concentration did not appear to be able to reverse the activation by fructose 1,6-bisphosphate. 5. In the presence of a low concentration of phosphoenolpyruvate, increasing the concentration of the product, ATP, caused an initial increase in enzyme activity, followed by an inhibitory phase. In the presence of either fructose 1,6-bisphosphate or L-alanine only inhibition was seen. 6. The inhibition by ATP could not be completely reversed by fructose 1,6-bisphosphate.

An investigation of the interactions of the allosteric modifiers of pyruvate kinase with the enzyme from Carcinus maenas hepatopancreas