Question

14.) (s pos) CAJ The tartness of some wines is due to high concentrations of -matate. Draw out the sequence of reactions showing how veast cells synthesize the net production of L-malate from pyruvate under anaerobic conditions without any net NADH production. Show the structures and names of all reactants and products, as well as the names of the enzymes. You do not need to draw the structures of ATP, NAD, COA, etc., but do show them as reactants or products in the appropriate places. You do not need to show the mechanisms of the enzymes.

Answer 1

Ans) Malic acid is a potential biomass-derivable “building block” for chemical synthesis. Since wild-type Saccharomyces cerevisiae(Yeast cells) strains produce only low levels of malate, metabolic engineering is required to achieve efficient malate production with this yeast. A promising pathway for malate production from glucose proceeds via carboxylation of pyruvate, followed by reduction of oxaloacetate to malate. This redox- and ATP-neutral, CO₂-fixing pathway has a theoretical maximum yield of 2 mol malate (mol glucose)

o=P-o- H₂C=c-c-o (Phosphoenol pyruvate) Pyruvate LATP kinase WADP tpi H₂Cc-c-o (Pyruvate) Pyruvate LATP Carboxylase J ADP C-CH2 -CH2 Quo Ostaloautate

Oye-c-CH2-Co [oxalo acetate] Malate I NADH Y NA Dehychogen / сле C-&- CH₂-c00- C-CH₂-Coo OH 1-Malate

• Phosphoenolpyruvate carboxylase (also known as PEP carboxylase, PEPCase is an enzyme in the family of carboxy-lyases found in plants and some bacteria that catalyzes the addition of bicarbonate (HCO₃⁻) to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate and inorganic phosphate.
• PEP + HCO₃⁻ → oxaloacetate + Pi
• Oxaloacetate to L-Malate synthesis reaction:
• It is a NAD+ dependent reaction
• Reaction is pulled in forward direction by next reaction(Citrate synthase) as OAA is depleted at a very fast rate.
• OAA is converted to Malate in the presence of Malate dehydrogenase enzyme to form L-Malate.

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