BIO SCI 98 Lecture Notes - Lecture 7: Covalent Bond, Cell Growth, Hemoglobin
14 Jul 2018
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• Pg. 225–229 : (6.5 part): Regulatory Enzymes
o Groups of enzymes work together in pathways to carry out a given metabolic
process - such as multi-reaction breakdown of glucose to lactate or multi-reaction
synthesis of amino acid from simpler precursors
o Regulatory enzymes: increased or decreased catalytic activity in response to certain
signals
• Adjustments in the rate of reactions catalyzed by regulatory enzymes and
therefore in the rate of entire metabolic sequences allow the cell to meet
changing needs for energy and for biomolecules require in growth and repair
▪ In most multi-enzyme systems: the first enzyme of the sequence is a
regulatory enzyme
o Allosteric enzymes: function through reversible, non-covalent binding of regulatory
compounds called
• Allosteric modulators
• Allosteric effectors: generally small metabolites or cofactors
• Covalent modification
o Cell growth and survival = dependent on efficient use of resources/regulatory
enzymes
o Allosteric Enzymes Undergo Conformational Changes in Response to Modulator
Binding
• Allosteric proteins: those having "other shapes" or conformations induced by
the binding of modulators
▪ May be inhibitory or stimulatory
▪ Homotropic: regulatory enzymes for which substrate and modulator are
identical
• Ex. Hemoglobin binding of the ligand (substrate) in the cause of
enzymes causes conformational changes that affect the subsequent
activity of other sites on the protein
▪
• Allosteric enzymes are generally larger and more complex than non-allosteric
enzymes
▪ Most have two or more subunits
o The Kinetic Properties of allosteric Enzymes Diverge from Michaelis-Menten Behavior
• Allosteric enzymes show relationships between Vo and [S] differ from Michaelis-
Menten kinetics
