WHAT IS -VE AND +VE ALLOSTERIC MODULATION??

Allosteric regulation is the regulation of an enzyme or other protein by binding of an effector molecule at the protein's allosteric site. Allosteric site of protein is another pocket or crevice other than its active site to which an effector molecule can bind. Effectors can either enhance or inhibit the activity of the enzyme. Effectors that enhance the protein's activity are called allosteric activators and those who inhibit are called allosteric inhibitors.

Positive modulation

when an allosteric activator gets attached to the allosteric site of the enzyme.

It enhances the attraction between substrate molecules and activation site. 

Negative modulation

when an allosteric inhibitor gets attached to the allosteric site of the enzyme.

It decreases the affinity for substrate at the active site. 

Try to understand from the diagram. The positive sign indicates positive modulation while the negative sign indicates negative modulation.

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