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Biosynthesis Flashcards

1
Q

Primary metabolites

A

Trophophase
Metabolism products required for growth and the maintenance of cellular function
e.g. amino acids, fatty acids, nucleoside, vitamins, carbohydrates

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2
Q

Secondary metabolites

A

Idiophase
The end products of primary metabolism that are non-essential for cell growth/maintenance, but can be important in other cellular activities
e.g. steroids, alkaloids, antibiotics, toxins

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3
Q

Fatty acids

A

Long alkyl chain with carboxylic acid group

Alkyl chain is generally unbranched, even no. of carbons, can be unsaturated (only ‘cis’ alkenes)

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4
Q

C14 chain length

A

Myristic acid

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5
Q

C16 chain length

A

Palmitic acid

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6
Q

C18 chain length

A

Stearic acid

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7
Q

Reasons for thioester instead of normal ester in acetyl coenzyme A

A

S is a better nucleophile than O, so is easier to acetylate
Thioesters are more reactive to hydrolysis than esters (less significant resonance structure so resemble ketones, which are more reactive than esters)

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8
Q

Structure of acetyl coenzyme A

A

Draw

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9
Q

Synthesis of acetyl groups for acetyl coenzyme A

A

Draw
Step 1: Glucose + 2NAD+ + 2Pi + 2ADP —> 2 pyruvate + 2 NADH + 2ATP + 2H+ + 2H2O
Step 2: Pyruvate decarboxylation

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10
Q

NAD(P)+/NAD(P)H

A

The primary cofactors used for oxidation and reduction in biosynthesis
Draw

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11
Q

NAD(P)+

A

Oxidising agent

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12
Q

NAD(P)H

A

Reducing agent

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13
Q

Biotin

A

Nature’s carrier for CO2

Draw

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14
Q

BCCP

A

Biotin carboxyl carrier protein

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15
Q

Synthesis of malonyl coenzyme A

A

Acetyl coenzyme A can be carboxylated by carboxybiotin to give malonyl coenzyme A
Draw

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16
Q

Fatty acid biosynthesis

A

Draw

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17
Q

FAS

A

Fatty Acid Synthase

Reacts with acetyl coenzyme A in fatty acid biosynthesis

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18
Q

ACP

A

Acyl Carrier Protein

Reacts with malonyl coenzyme A in fatty acid biosynthesis

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19
Q

How is the growing fatty acid chain cleaved from ACP?

A

By a thioesterase

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20
Q

How does synthesis of unsaturated fatty acids occur?

A

Re-oxidation of the fatty acid chain by a “dithio-linked” enzyme
2 Enz-SH + 1/2O2 —> Enz-S-S-Enz + H2O

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21
Q

Terpenes

A

Hydrocarbons (few heteroatoms, but sometimes oxygenated)
Can contain unsaturation
Often polycyclic
Built from isoprene units

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22
Q

Isoprene

23
Q

C10 terpenes

A

Monoterpenes
Comprise 2 isoprene units
Alpha/beta-pinene, camphor

24
Q

C15 terpenes

A

Sesquiterpenes
Comprise 3 isoprene units
Artemisin, juvabione

25
C20 terpenes
Diterpenes Comprise 4 isoprene units Gibberellin A3, taxol (= hybrid natural product with terpene core)
26
C30 terpenes
Triterpenes Comprise 6 isoprene units Cholesterol, beta-amyrin
27
Why does nature not use isoprene for terpene synthesis?
Isoprene is a gas
28
What does nature use for terpene synthesis?
IPP (isopentenyl pyrophosphate) | DMAPP (dimethylallyl pyrophosphate)
29
Pyrophosphate
2 phosphate groups joined together
30
Lovastatin
Drug for the treatment of high blood cholesterol | Inhibits HMG-CoA reductase, which catalyses the RDS for the whole biosynthetic route to cholesterol
31
Uses of monoterpenes
Monoterpenes = low molecular weight and low polarity so often volatile Have characteristic odours so often used as perfumes/fragrances/flavourings
32
Synthesis of sesquiterpenes
Geranyl pyrophosphate + IPP ---> farnesyl pyrophosphate
33
Synthesis of diterpenes
Farnesyl pyrophosphate + IPP ---> geranylgeranyl pyrophosphate
34
Synthesis of triterpenes
Synthesised from squalene, which is synthesised from 2 farnesyl units in a "head to head" fashion
35
What is squalene used in?
The synthesis of steroids Starts with the formation of 2,3-oxidosqualene, which then undergoes electrophilic cyclisation and rearrangement to access the 'steroidal nucleus'
36
Polyketides
Highly oxygenated - often a pattern to the oxygenation with an O on every other C Generally involve rings (often aromatic, but not always) Biosynthetically related to fatty acids
37
Biosynthesis of polyketides
(Draw biosynthesis of orsellinic acid) | First part is the same as for fatty acids minus the 3 steps after the Claisen ester condensation
38
Structure of orsellinic acid
(draw)
39
O-Methylation of polyketides
Carried out by S-adenosylmethionine (SAM) = methionine linked to the nucleoside adenosine Provides a source of electrophilic Me
40
Structure of S-adenosylmethionine
Draw
41
Elucidation of polyketide synthesis
Using doubly-labelled acetate Will be incorporated into doubly-labelled acetyl-CoA by the species Collect polyketide product from organism and run {1H}-13C NMR Will see coupling between the two 13Cs to give doublets Each doublet will have a coupling constant that will be the same for both carbons in a coupling pair (i.e. both from the same acetate unit), so we can figure out which 2 carbons came from the same acetate unit
42
Why does the quantity of doubly-labelled acetate need to be carefully controlled?
So the species is using a mixture of doubly-labelled and non-labelled acetyl-CoA for biosynthesis Ideally need to be statistically most likely to end up with one doubly-labelled acetate unit per molecule of polyketide product
43
Alkaloids
Structurally diverse All contain a basic nitrogen (called 'alkaloids' because they behave like alkali) Mostly derived from amino acids
44
Useful property of the basic nitrogen in alkaloids
Enables their isolation from other natural products Can carry out an acidic aqueous extraction of the plant/animal matter, followed by neutralisation then back-extraction into an organic solvent
45
Pyridoxal phosphate
``` (draw) Can carry out a variety of functional group interconversions: Amine --> ketone Ketone --> amine Racemisation of alpha-amino acids Decarboxylation of alpha-amino acids Amino acid --> aldehyde ```
46
Amine --> ketone
i.e. amino acid ---> alpha-ketocarboxylic acid Process can also operate in the opposite direction because all steps are equilibria i.e. can transform alpha-keto acid into an alpha-amino acid
47
Shikimic acid
(Draw) Shikimic acid is an important biosynthetic precursor to the aromatic amino acids: Phe, Tyr, Trp Also the precursor to the flavonoids Starting material for the manufacture of Tamiflu Precursor for the K vitamins and chloramphenicol
48
Biosynthesis of shikimic acid
(Draw) Starts with phosphoenol pyruvate Names of some intermediates: shikimate, chorismate, prephenate
49
Pathways for the conversion of prephenate into Phe and Tyr
Redox-neutral Requires oxidative step (draw)
50
Biosynthesis of cocaine
Draw
51
Alpha amino acid racemisation
Draw
52
Decarboxylation of alpha amino acid
Draw
53
Alpha amino acid to aldehyde
Draw

Biosynthesis (2 decks)

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