For my sins I worked in NHS biochemistry for a while at St Mary's Praed Street. Although the laboratory was a diagnostic, ie not research lab, we did do investigations to see if we could improve both the specificity and sensitivity of the analyses we performed. This was in addition to improving the reliability and reproducibility of our results.Simply, were our results of any use and were they accurate?One of the tasks I got was the investigation of sigmoid kinetics of allosteric enzymes.Briefly an enzyme is a protein that catalyses a chemical reaction and does not change as a result of that reaction.Each enzyme has a specific substrate, what it acts on, and specific products, what the results of the reaction are.An example, sucrase - which splits sucrose into glucose and fructose. That's all it does, nothing else.Basically an allosteric enzyme is an enzyme whose efficiency of operation is based on an effector which is often separate from its substrate. The efficiency rises proportionately to the effector until maximum efficiency is reached. After this point no further efficiency is achieved regardless of increase of effector. The plot so obtained on a graph is similiar to a stretched "S", hence the sigmoid bit.In the lab I was investigating glycogen phosphorylase part off the ATP cycle.In day to day terms imagine a donkey attached to a cart.The two coupled together are the enzyme. The function in this case is to move olives, for instance, from one location to another (the product of the reaction).The cart is loaded with olives. The donkey does not move.To start the donkey an effector is required. The donkey is tapped with a stick, the effector. The donkey moves slowly forward. It is tapped harder and more frequently, ie the concentration of the effector is increasing. Eventually the donkey will be moving at its maximum speed regardless of how often its tapped, or at least the speed required. When the donkey arrives at the destination by reducing the intensity of tapping it will slow and stop.Of course the ensemble could be stopped by applying the cart's brakes, and some enzyme reactions work like that too.I hope that explanation hasn't killed the interest of any budding enzymologists out there!As my boss used to say: "If physics is the king of science, then biochemistry is the queen!"
Alan Brainsby ● 6533d