There are two kinds of aldolases. Class I aldolases are found in animals and plants, whereas class II aldolases are found in fungi, algae, and some bacteria.Only class I aldolases form an imine. Class II aldolases have a metal ion (Zn2 + ) at the active site. The mechanism for catalysis by class I aldolases wasdescribed in Section 22.13. Propose a mechanism for catalysis by class II aldolases.

There are two kinds of aldolases. Class I aldolases are found in animals and plants, whereas class II aldolases are found in fungi, algae, and some bacteria.Only class I aldolases form an imine. Class II aldolases have a metal ion (Zn2 + ) at the active site. The mechanism for catalysis by class I aldolases wasdescribed in Section 22.13. Propose a mechanism for catalysis by class II aldolases.

Organic Chemistry

9th Edition

ISBN:9781305080485

Author:John E. McMurry

Publisher:John E. McMurry

Chapter20: Carboxylic Acids And Nitriles

Section20.SE: Something Extra

Problem 27MP: Naturally occurring compounds called cyanogenic glycosides, such as lotaustralin, release hydrogen...

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There are two kinds of aldolases. Class I aldolases are found in animals and plants, whereas class II aldolases are found in fungi, algae, and some bacteria. Only class I aldolases form an imine. Class II aldolases have a metal ion (Zn2+) at the active site. Propose a mechanism for catalysis by class II aldolases.
Naturally occurring compounds called cyanogenic glycosides, such as lotaustralin, release hydrogen cyanide, HCN, when treated with aqueous acid. The reaction occurs by hydrolysis of the acetal linkage to form a cyanohydrin, which then expels HCN and gives a carbonyl compound. (a) Show the mechanism of the acetal hydrolysis and the structure of the cyanohydrin that results. (b) Propose a mechanism for the loss of HCN, and show the structure of the carbonyl compound that forms.
The formation of Br2 from NBS first involves the reaction of NBS with HBr to form an iminol intermediate and molecular bromine. The intermediate then undergoes acid-catalyzed tautomerism to form succinimide, the byproduct of the reaction. Propose a curved-arrow mechanism for the conversion of NBS into succinimide that also accounts for the formation of Br2.
One of the later steps in glucose biosynthesis is the isomerization of fructose 6-phosphate to glucose 6-phosphate. Propose a mechanism, using acid or base catalysis as needed.
Ethanolamine ammonia lyase, a coenzyme B12–requiring enzyme, catalyzes the following reaction. Propose a mechanism for this reaction.
To solve this problem, you need to read the description of the Hammett s, r treatment given in Chapter 15, Problem 92. When the rate constants for the hydrolysis of several morpholine enamines of para-substituted propiophenones are determined at pH 4.7, the r value is positive; however, when the rates of hydrolysis are determined at pH 10.4, the r value is negative.a. What is the rate-determining step of the hydrolysis reaction when it is carried out in a basic solution?b. What is the rate-determining step of the hydrolysis reaction when it is carried out in an acidic solution?
Polyunsaturated fatty acids (PUFA's) in oils 0.g. sunflower oil are prone to rancidity because they contain conjugated double bond systems which are easily oxidized in the presence of light or peroxides. BHT Is used as an antioxidant in oils to prevent oxidative rancidity. How do BHT prevent oils from reacting with peroxides so that they do not become rancid? Show the mechanism.
Ticlopidine is an antiplatelet drug used to prevent strokes. Draw an alkyl halide and choose the conditions that would promote an SN2 reaction to yield this intermediate in the synthesis of ticlopidine.
The following transformation involves a series of four consecutive Heck reactions and the formation of the four-ring steroid nucleus (Section 26.4) as a racemic mixture. Propose structural formulas for the palladium-containing intermediates involved in this reaction.
In dilute aqueous base, (R)-glyceraldehyde is converted into an equilibrium mixture of (R,S)-glyceraldehyde and dihydroxyacetone. Propose a mechanism for this isomerization.
The start drug is Tolbutamide and the product is Chlorpropamide. Which of the following is incorrect? a. the -CH3 groyp is replaced with Cl atom to prevent oxidation of –CH3 group b. The -CH3 group in Tolbutamidw can be easily oxidized into -CH20H, and then to –CO2H c. this modification is used to prolong the duration of action of chlorpropamide d. this modification is achieved by an oxygen enzyme e. none of the above
Imidazoleglycerol‑phosphate dehydratase is an enzyme in the histine biosynthesis pathway. It catalyzes the E1 dehydration of D‑erthyro‑imidazole‑glycerol phosphate to imidazole acetol‑phosphate. This is a rare example of a biological E1 reaction, as most biological elimination reactions occur through E1cB instead. In this reaction, D‑erthyro‑imidazole‑glycerol phosphate is first protonated to form a good leaving group. Then, the leaving group is ejected to form the resonance‑stabilized carbocation shown. Draw curved arrows forming the most stable resonance structure to explain why this reaction goes through an E1 mechanism. Draw curved arrows to form the most stable resonance structure.