Lecture 30 - Fatty Acid Biosynthesis 2

Question 1

What is a key regulatory step

Answer 1

Biotin is an essential co-enzyme – it is covalently linked to a lysine residue via the ε–amino group
Mechanism is like that of pyruvate carboxylase

Question 2

What are the 3 components in an E.Coli Enzyme

Answer 2

Biotin carboxyl carrier protein BCCP

Biotin carboxylase

Carboxyltransferase

Question 3

How are animal enzymes different from bacterial enzymes

Answer 3

Quite different – a single multifunctional protein.
Mr of 265 000 (rat liver enzyme)

Found as a dimer with one biotin per subunit.

Non-functional as a dimer and must polymerise to be active – more on this in next lecture

Question 4

How is substrate linkage efficient in enzymes

Answer 4

Intermediates are not released

Makes it much more efficient

There are two points of linkage of substrates to Fatty acid synthase

Question 5

What is an example of an acting attachment site ???

Answer 5

 ketoacyl ACP synthase
the -SH group of a cysteine amino acid residue of this protein acts as an attachment site for the priming group, acetyl from acetyl-CoA and also holds the longer acyl chain before the condensation with malonyl-ACP

Question 6

What is the attachment site on an ACP

Answer 6

the attachment site here is the –SH group of a 4-phosphopantetheine which is in turn linked to a serine side chain of ACP.

Question 7

What is the final product of FA synthesis in Yeast enzyme

Answer 7

Predominantly released as palmitoyl-CoA

ie the palmitate is transacylated onto CoA from ACP rather than hydrolysed to free fatty acid

Question 8

What is the final product of FAS in bacterial/plant enzyme

Answer 8

About 20% is released as palmitoyl-CoA or palmitoyl-ACP

About 70% is released as vaccenate-CoA C18:1 11

Question 9

What are some other requirements for FAS

Answer 9

CYTOSOLIC acetyl-CoA is the precursor of F.A. synthesis

Acetyl-CoA is synthesised in the mitochondria
- needs to get out into the cytosol

A transport system is required