Health and safety: 4-nitrophenol is harmful.
Introduction:
Enzymes are quaternary structured proteins that are specific biological catalysts that speed up a reaction without being used up. They contain an active site that allows substrate to bind to a specific area on the enzyme which is of a complimentary shape of the substrate. There are two models of enzyme action, the Lock and Key model and the Induced Fit model. The Lock and Key model states that the enzyme has a specific active site shape wherein the substrate fits like a key. However the Induced Fit states that the enzyme has a specific active site shape and the substrate has a complimentary shape. The enzyme slightly adjusts the shape of its active site and moulds around the substrate. This is the accepted theory. The equation is: enzyme + substrate enzyme-substrate complex enzyme + product.
Enzyme assays measure the loss of the substrate or the formation of product. Phosphates are found in the soluble and lysosomal fractions of cells. An enzyme assay can be classified by the pH at their maximum activity, acid and alkaline phosphatases which includes 4-nitrophenyl phosphate. The 4-nitrophenyl phosphate is colourless, whereas the product 4-nitrophenol is yellow in colour after hydrolysis. Phosphatases are characterised by their ability to hydrolyse a phosphate group from the phosphate ester, producing an alcohol and phosphoric acid. The enzyme being studied is alkaline phosphatase; this is a widely distributed enzyme that can hydrolyse a variety of phosphate esters. There are many factors that can affect enzyme assay such as incubation period of the enzyme and substrate under appropriate conditions.
Aims: To explain the principals behind the handling of enzymes and the assay and to calculate the activity of an enzyme.
Results:
Tube Number
1
2
3
4
5
6
Amount of 4-nitrophenol required (mol)
0.0
0.2
0.4
0.6
0.8
1.0
4-nitrophenol cm3 (1 mol cm-3)
0.0
0.2
0.4
0.6
0.8
1.0
Water,