Are the following examples of general acid/base catalysis, covalent catalysis, c

Question

Are the following examples of general acid/base catalysis, covalent catalysis, catalysis by approximation (proximity effect), or metal-ion catalysis? Complete parts a, b, c, and d.

a)

(b) NMP kinases bring two nucleotides, for example AMP and ATP, together to facilitate the transfer of a phosphoryl group from one nucleotide to the other (creating two ADP). The enzyme positions the adenosine triphosphate (ATP) such that the gamma phosphate group is placed adjacently to the phosphate group of the NMP kinase. This facilitates the transfer of the phosphate between the two molecules.

(c) In aspartate ammonia lyase, a deprotonated serine sidechain performs a nucleophilic attack on a carbonyl carbon of the substrate.

(d) An active site histidine abstracts a proton from a substrate, making it more reactive, then donates the proton back to the product.

Explanation / Answer

a) This reaction is a example of metal ion calalysis in which Zinc ion coordinate with oxygen atom of carbonyl and facilitates tha attack on carbonyl carbon.

b) Magnesium atom of NMP kinases bind with the two phosphoryl groups covalently which facilitates the transfer of one phosphoryl group from one nucleotide to another. Thus this is a example of cavalent catalysis.

c) Aspartate ammonia lyase abstracts the proton from serine sidechain which then engaged in the nucleophilic attack on carbonyl carbon. Thus this is a example of acid base catalysis.

d) An active site histidine abstracts the proton from substrate and donate it to the product. Thus this is also a example of   acid base catalysis

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