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• The rate of reaction of an enzyme is described by the Michaelis-Menten equation:

• The rate of the reaction can therefore be increased by:
• Changing substrate concentration
• Changing enzyme concentration
• Changing V_max
• Changing K_M


• Sometimes enzyme activity is increased directly by positive allosteric modulation
• For example, insulin binding to its receptors increased the activity of the tyrosine kinase portion of the receptor
• This tends to either increase K_M or V_max


• Other enzyme activity is increased indirectly via intermediate messengers
• For example, G-protein coupled receptors whose alpha subunit increases the activity of adenylyl cyclase e.g. β-adrenoreceptors, D₁ receptors, H₂ receptors

Increased enzyme concentration