| Abstract: | An allosteric model of phosphorylase B is proposed based on the following assumptions. The enzyme consists of two sub-units and undergoes a concerted transition from the inactive T to the active R state. The binding of substrates, phosphate, and glycogen is regarded as exclusive, but the binding of the activator AMP is nonexclusive. The enzyme model is of the K, V type, i. e., the activator AMP is important, not only for the T-R transition and the substrates binding, but also for the formation of the active site. Therefore, it displays a big influence on the maximal reaction rate. Calculations based on this model lead to an equation containing 5 constants, which can be easily computed from kinetic data. All kinetic measurements fit the expressions derived from the model. Independent methods for the measurement of all the constants involved were developed. They are based on the study of binding of phosphorylase with the substrates and the activator. These measurements are in satisfactory agreement with the data obtained from enzyme kinetics. |
