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#enzyme knockout

2 public questions tagged with this topic.

Gene Dissection and Complementation

In a pathway A→B→C→D, if enzyme B is knocked out and enzyme C is overexpressed, growth requires

In pathway A→B→C→D where enzymes named for products knockout of early enzyme B prevents synthesis of B and consequently substrate for downstream steps C and D. Overexpressing enzyme C converting C to D cannot rescue because substrate C never produced; pathway remains blocked upstream despite increased catalytic potential downstream. No endogenous downstream intermediates exist to drive flux so cell auxotrophic. Only complete medium supplying final product D plus all other growth factors bypasses entire endogenous biosynthesis restoring growth. This illustrates epistasis of early block over lat

Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 14: Pathway Block Epistasis Over Overexpression Rescue

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Gene Dissection and Complementation

Knockout of an essential enzyme in a biosynthetic pathway results in

Knockout of essential enzyme encoding committed step eliminates catalytic conversion preventing formation of downstream metabolite required for growth. Without gene product intermediate before block accumulates while product downstream depleted causing auxotrophy or lethality depending on essentiality and alternative routes. Growth on minimal medium fails unless final product supplied exogenously through medium. Such loss-of-function phenotype directly links gene to metabolite demonstrating causality in biochemical pathway. Complete deletion produces more severe effect than missense often full

Ref: Hartl & Ruvolo, Genetics, 6th ed., Chapter 14: Essential Enzyme Knockout Decreases Product Formation

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