Question

RNAase, the enzyme that catalyzes the hydrolysis of RNA, has two catalytically active histidine residues at its active site. One of the histidine residues is catalytically active in its acidic form, and the other is catalytically active in its basic form. Propose a mechanism for RNAase.

Short answer

There are four types of nitrogen bases that are adenine (A), guanine (G), cytosine C),

and uracil (U) present in RNA.There are three types of RNA these are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). All three types of RNA are involved in protein synthesis.

Step-by-step solution

Step 1:RNA and its types

There are four types of nitrogen bases that are adenine (A), guanine (G), cytosine C),

and uracil (U) present in RNA.There are three types of RNA these are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). All three types of RNA are involved in protein synthesis.

Mechanism of RNAase

In the given reaction in the first step, the imidazole ring of one histidine act as a general base catalyst, removing the proton of the -OH to make it a better nucleophile. The imidazole ring of other histidine acts as a general acid catalyst, protonating the leaving group to make it a weaker base and therefore a better leaving group. In the second step of the reaction, the role of the two imidazole rings is reversed.

Mechanism of RNAase