Synthesis of isoprenoid compounds

Synthesis of isoprenoid compounds

1. Synthesis of Isoprenoid Compounds Presented by: Qudsia rehman Noor ul huda Mutayyba fatima

2. Isoprenoids Isoprenoids are a family of natural products whose structures are composed of five-carbon isoprene units. The unit consists of a four-carbon chain with a one-carbon branch at carbon 2. Isoprene unit C5

3. Isoprene : 2-methylbuta-1,3-diene

4. Terpenoids is formally derived from isoprene units and are sometimes called isoprenoids . The name terpene was given to hydrocarbons which were detected in terpentine oil. Terpenes are known as the large group of hydrocarbons made up of isoprene units (C5H8).

5. Classification of terpenoids is based on number of isoprene units

6. Biosynthesis: Step 01: The precursor molecule for the synthesis of isoprenoid derivatives is  Hydroxymethylglutaryl -coenzyme A (HMG- CoA ) . It is formed  formed by condensation reaction between acetyl- CoA and acetoacetyl-CoA , catalyzed by  HMG- CoA Synthase .

7. Step 02: Mevalonate   is then formed in a reaction catalysed by the enzyme  HMG- CoA Reductase ,  which is an integral protein of endoplasmic reticulum membranes. The  carboxyl  group of hydroxymethylglutarate that is in ester linkage to the thiol of coenzyme A is reduced to an  aldehyde  and then to an  alcohol . NADPH  acts as a reductant in this 2-step reaction:

8. Step 03: Mevalonate  is phosphorylated by 2 sequential phosphate transfers from ATP, before ATP-dependent decarboxylation , with dehydration, yields  isopentenyl pyrophosphate :

9. Step 04: Isopentenyl Pyrophosphate Isomerase  inter-converts isopentenyl pyrophosphate and  dimethylallyl  pyrophosphate  via a mechanism involving deprotonation and protonation . Prenyl Transferase   then catalyzes a series of head-to-tail condensation reactions. Dimethylallyl pyrophosphate reacts with isopentenyl pyrophosphate to form  geranyl  pyrophosphate .  Reaction of this compound with another isopentenyl pyrophosphate produces  farnesyl pyrophosphate :

10. Step 05: Squalene Synthase  catalyzes tail to tail condensation of 2 molecules of farnesyl pyrophosphate, with reduction by NADPH, to yield  squalene .