The Chemistry of Nucleic Acid Biosynthesis Describe three...

Key Concepts

Template-Directed Nucleic Acid Synthesis

A common feature among DNA polymerase, RNA polymerase, reverse transcriptase, and RNA replicase is that they perform template-directed polymerization. This means that these enzymes use an existing nucleic acid strand as a guide for incorporating complementary nucleoside triphosphates to form a new strand, ensuring accurate and specific base pairing during nucleic acid biosynthesis.

Nucleotidyl Transfer Reaction Mechanism

The underlying chemical reaction catalyzed by these enzymes involves the nucleophilic attack by the 3'-hydroxyl group of the growing nucleic acid chain on the alpha phosphate of an incoming nucleoside triphosphate. This reaction produces a phosphodiester bond while releasing pyrophosphate, a mechanism that both drives the reaction forward and contributes to the fidelity of synthesis.

Role of Divalent Metal Ions

Another shared property is the requirement for divalent metal ions, such as Mg2+, which act as essential cofactors. These ions assist in aligning substrates, stabilizing negative charges, and facilitating the catalysis of bond formation by lowering the activation energy, which is critical for the efficiency and accuracy of the polymerization process.

Template Independence and Phosphorolytic Activity of Polynucleotide Phosphorylase

Polynucleotide phosphorylase is similar to the polymerases in that it catalyzes the formation of phosphodiester bonds, but it differs by not requiring a template for its polymerization reaction. Instead of using water to drive condensation reactions, it utilizes inorganic phosphate, making its reaction reversible. This template independence and reversible phosphorolysis mechanism set it apart from its template-dependent counterparts.

Transcript

00:01 Okay, so let's quickly check out problem number six from chapter 26.

00:05 We have been given some enzymes in the question and we have been asked to find out the similarities, differences and the commonality between these enzymes.

00:17 So let us see what are these enzymes.

00:21 So the first enzyme is dna polymerases.

00:26 Second enzyme is rna polymerases.

00:30 And the third enzyme is, reverse transcriptase, reverse transcriptase enzyme.

00:42 Next enzyme is rna replicase.

00:49 And another enzyme is, another and the last enzyme is polynucleotide phosphorylase.

01:05 The next enzyme is polynucleotide phosphorylase.

01:08 So we will decipher about, we will learn about its functions, the functions of these enzymes and the differences and the commonality and the similarities of all of these.

01:25 So the first run being rna polymerase, right? so rna polymerase helps in, it helps in building up the nucleotides.

01:37 More specifically, dna nucleotides.

01:40 So more specifically, it helps in building up dna spritz.

01:45 And talking about its functionality, it has beta clamp.

01:52 It improves the processivity.

01:54 It is a very fast enzyme.

01:57 As in it is a very, it is non -fiddle.

02:02 There's non -fiddle and it works really fast.

02:07 This thing, it adds up the nucleotides, dna polymerase, it adds up the nucleotides at a much faster rate.

02:16 So it has a very high processivity.

02:19 That's its first function.

02:22 And the second is, and the second important function is that it has dna directed dna synthesis.

02:29 It functions on the basis of dna directed dna synthesis.

02:33 That is, it will require dna as a template.

02:39 As a template strand, there should be a dna upon which it can replicate or it can synthesize basically.

02:46 So synthesis of dna polymerase, the function of dna polymerase is to synthesize the nucleotides and it synthesizes on the basis of the direction of dna or the dna template.

03:00 So those are the two functions of dna polymerase.

03:04 Now coming to the second enzyme rna polymerase, its first function is that they are actually loaded by a promoter and they are loaded by a, they are loaded by, the proteins at a promoter.

03:18 So it will require a promoter or something like p, a promoter to for its further function, for it to synthesize the rna, for it to synthesize the nucleotides.

03:32 So this rna polymerase is an important enzyme in case of transcription.

03:38 Dna replication is an important enzyme in case of replication.

03:44 Dna polymerase helps in replication of replication dna rna polymerase helps in transcription in it helps in building up the m rna transcript and the substrates are the nucleosite 5 prime tryphosphates in case of dna polymerase the substrates here in case of dna polymerase it is a dna directed synthesis right and in case of rna polymerase the substrates are nucleosite 5 prime tryphosphates now talking about the third and which is reverse transcriptase enzyme.

04:21 So this enzyme, as the name suggests, it is like a retrovirus in case of this is the thing which happens in retroviruses.

04:31 This enzyme reverse transcriptase is mainly found in retroviruses.

04:36 All right...

Please give Ace some feedback