Chapter 7 Regulation of Gene Expression Regulation of Enzyme Activity Constitutive enzymes Enzymes induced by specific circumstances Two major modes of regulation in the cell Control the activity of preexisting enzymes Control the amount of an enzyme
Chapter 7 Regulation of Gene Expression Regulation of Enzyme Activity – Constitutive enzymes – Enzymes induced by specific circumstances Two major modes of regulation in the cell – Control the activity of preexisting enzymes – Control the amount of an enzyme
Regulation can be performed in gene expression and enzyme activity level Regulated Components of Metabolism DNA、X Transcription mRNA Tra anslation Protein (enzyme) Catalysis Regulation of enzyme activity Compound A Compound B
Regulation can be performed in gene expression and enzyme activity level
Inhibition Types Feedback inhibition the activity of the first enzyme of the pathway is inhibited by the end product Covalent modification The activity of an enzyme is affected by attachment of the nucleotide adenosine mono phosphate(AMP)or adenosine diphosphate(ADP) attachment of inorganic phosphate methylation
Inhibition Types Feedback inhibition – the activity of the first enzyme of the pathway is inhibited by the end product. Covalent modification – The activity of an enzyme is affected by • attachment of the nucleotide adenosine monophosphate (AMP) or adenosine diphosphate (ADP) • attachment of inorganic phosphate • methylation
Regulation of Transcription Regulation of transcription: regulation of enzyme synthesis Induction: the synthesis of an enzyme only when its substrate is present Repression: no enzyme synthesis in the presence of its product Example, The lac operon
Regulation of Transcription Regulation of transcription: regulation of enzyme synthesis: – Induction: the synthesis of an enzyme only when its substrate is present – Repression: no enzyme synthesis in the presence of its product Example; The lac operon
Example: Diauxic Growth Diauxic growth on mixture of glucose and lactose(The lac operon
Example: Diauxic Growth Diauxic growth on mixture of glucose and lactose (The lac operon)