Fumarase Essay Exam

Enzyme name and pathway

• fumarase/fumarate hydratase

• citric acid cycle/TCA cycle/Krebs cycle

• takes place in mitochondria

• essential for aerobic energy production in cells

• pathway produces oxaloacetate to use in the next phase of the cycle, CO2, NADH and FADH2 to be used in oxidative phosphorylation

Type of catalyzed reaction

• reversible hydration/dehydration reaction

• adds water molecule across carbon-carbon double bond

• trans double bond in fumarate

• conversion to L-malate

• reactant is water, substrate is fumarate, malate is product 

Intermediates and cofactors

• no cofactors or prosthetic groups

• carbanion intermediate (stabilized by enzyme active site)

Catalysis mechanisms

• acid-base catalysis

• water (nucleophile) attacks doble bond

• hydroxyl is added to one carbon and hydrogen is added to adjacent carbon

• active site is conserved

• His and Asp act as acid base pair to transfer proton

• Glu stabilizes negative intermediate

• Ser and Thr form hydrogen bonds with carboxyl groups to hold it in the right orientation

Regulation of activity

• based on substrate availablilty

• high levels of ATP - citric acid cycle slows down so concentrations of fumarate decrease )fumarase activity decrease)

• low levels of ATP and high ADP - opposite is true

• because reversible high levels of product (malate) will compete with substrate and cause inhibition (feedback inhibition)

Deficiencies and their effects

• mutations in FA gene that encodes fumarase enzyme

• buildup of fumarate

• disruption in the citric acid cycle

• neurological symptoms (developmental delay, poor muscle tone, seizures)

• also linked to factor (hereditary leiomyomatosis and renal cell cancer) - build up of fumarate promotes tumor growth.

Related nutritional factors (helpful or harmful)

• no specific dietary cofactors

• function is dependent on overall mitochondrial function needs snutritional factors

• iron, riboflavin, niacin, coenzyme Q (vitamins basically)