Fundamentals of Molecular Biology - V.I. Rezyapkin 2009

Transcription
Non-template RNA synthesis

There are Enzymes capable of synthesizing RNA in the absence of a template. These include polynucleotide phosphorylase and polyadenylate polymerase.

Polynucleotide phosphorylase is found in Bacteria and utilizes ribonucleoside 5’-diphosphates (NDPs) — ADP, CDP, GDP, and UDP — as substrates. This enzyme catalyzes a reaction that can be generally represented as follows:

Class="center">

The reaction is reversible. The enzyme catalyzes The formation of 3’-5’ phosphodiester bonds:

Polynucleotide phosphorylase cannot use NTPs and deoxynucleoside triphosphates as substrates for RNA Synthesis.

Polyadenylate polymerase mediates the Synthesis of the poly(A) tail at the 3’ end of mRNA. It uses ATP and RNA as substrates (Fig. 4.10).

Fig. 4.10. Polyadenylate polymerase synthesizes the poly(A) sequence at the 3’ end of mRNA

The enzyme catalyzes the formation of 3’-5’ phosphodiester bonds.

In Conclusion, it should be noted that METABOLISM/31.html">Transcription is one of the most complex biological processes, playing a central role in the expression of Genetic information. Numerous protein molecules take part in its execution.