Molecular and cellular biochemistry

The interaction of an extracellular agonist (First Messenger) with its plasma membrane receptor leads to the transmission of a signal across the cell membrane and results in the production and or activation of other signalling molecules (Second Messengers). These Second Messengers control the action of many protein kinases and protein phosphatases and so lead to cellular responses. Although the biochemical basis of the transduction of signals in the main signalling systems in eukaryotic cells is probably largely known, intensified research is ongoing in the following areas: the discovery of specific substrates for many protein kinases, elucidation of the biological significance of the differential tissue expression and heterogeneity of many signalling proteins, and the unravelling of diverse interactions (such as signal potentiation, synergism, antagonism and neuronal co-transmission) between signalling systems. As knowledge from such studies accumulates, it is becoming clear that the 'cross talk' interactions between signalling systems are important features of dynamic cell regulation. This special issue is designed to summarize some aspects of the current work on various Second Messenger Systems and the integration of signals with respect to plasma membrane receptors, Second Messenger generation and degradation, protein kinases and phosphatases, cell cycle control, and cellular learning and mememory (AU)

Biochemical aspects of ketogenesis, a review

Ketogenesis occurs only under certain physiological conditions, the physiological substrate for the process being long chain fatty acids. The condition for ketogenesis arises if the long chain fatty acid levels are high enough to render the liver incapable of metabolising all the acetyl CoA, formed as a result of hepatic oxidation of long chain fatty acids, via the tricarboxylic acid cycle to yield water and carbon dioxide. The state in which unesterified fatty acid levels are high enough to cause ketogenesis can be arrived at if there is a lack of insulin or a condition of starvation. Biochemical regulation, pathological condition and relative levels of ketone bodies are also reviewed. It was found that maximum ketonemia reflects not only increased production but also decreased use. The determination of urine or plasma 3-hydroxybutyrate may be of more importance than a simple urinary test upon ketone bodies in diabetic persons