The overall reaction rate for the bacterial RNA polymerase can be as fast as 40–50 nucleotides/ second at 37°C for most transcripts; this is about the same as the rate of translation (15 amino acids/sec), but much slower than the rate of DNA replication (800 bp/sec).

TLS Online TPP Program

#Id: 356

#Unit 1. Molecules and their Interaction Relevant to Biology

The reaction catalyzed by citrate synthase is essentially a Claisen condensation, involving a thioester (acetyl-CoA) and a ketone (oxaloacetate)

TLS Online TPP Program

#Id: 359

#Unit 1. Molecules and their Interaction Relevant to Biology

Eukaryotic cells have two isozymes of aconitase

• The mitochondrial isozyme (convert citrate to isocitrate in the citric acid cycle)

• The cytosolic isozyme 

TLS Online TPP Program

#Id: 360

#Unit 1. Molecules and their Interaction Relevant to Biology

The cytosolic isozymes has two distinct function, It catalyzes the conversion of citrate to isocitrate, providing the substrate for a cytosolic isocitrate dehydrogenase that generates NADPH as reducing power for fatty acid synthesis and other anabolic processes in the cytosol. It also has a role in cellular iron homeostasis

TLS Online TPP Program

#Id: 363

#Unit 1. Molecules and their Interaction Relevant to Biology

When cellular iron concentrations return to normal levels, IRP1 is converted to aconitase, and IRP2 undergoes proteolytic degradation, ending the low-iron response.

TLS Online TPP Program

#Id: 364

#Unit 1. Molecules and their Interaction Relevant to Biology

Pyruvate kinase acts in the nucleus to regulate the transcription of genes that respond to thyroid hormone. Glyceraldehyde 3-phosphate dehydrogenase moonlights both as uracil DNA glycosylase, effecting the repair of damaged DNA, and as a regulator of histone H2B transcription. 

TLS Online TPP Program

#Id: 366

#Unit 1. Molecules and their Interaction Relevant to Biology

The enzyme that catalyzes this reversible reaction is called succinyl-CoA synthetase or succinic thiokinase