Protein - Cysteine

Question 1

Cysteine

Answer 1

• Cysteine is a conditionally essential amino acid formed from methionine and serine in the liver (B6, B9 and B12 are needed).

Question 2

Direct food sources

Answer 2

• Direct food sources (most sulphur in food is in the form of protein-bound cysteine): legumes, sunflower seeds, eggs, chicken

Question 3

Cysteine as a component of other compounds

Answer 3

• It is a component of glutathione and is needed in the formation of Co-enzyme A and taurine.
• It is the rate-limiting amino acid for glutathione synthesis, so is very important for detoxification and antioxidant support

Question 4

Sulphate and liver detoxification

Answer 4

• Cysteine is the source of sulphate (-SO4), used in the phase II liver detoxification pathway sulfation (used for many drugs, steroid hormones etc.) increasing water solubility for their excretion.

Question 5

N-acetyl cysteine (NAC)

Answer 5

• N-acetyl cysteine (NAC) is a derivative of L-cysteine. It is used in supplementation as it is easier to absorb

Question 6

Function:
Liver Detoxification/
Antioxidant

Answer 6

Functions:
* It is a building block of glutathione. Cysteine plays a crucial role in the body’s antioxidant defences.
* Crucial in drug metabolism in the liver (drugs deplete glutathione, cysteine regenerates it)
Therapeutic uses:
* Liver support (including heavy metal detox)
* Healthy ageing support
* Ulcerative colitis

Question 7

Function:
Reproductive health

Answer 7

Functions:
* Has been shown to increase sperm concentration, likely due to its antioxidant properties
Therapeutic Uses:
* Infertility

Question 8

Function:
Respiratory health

Answer 8

Functions:
* Expectorant properties (it breaks up mucus to aid easier elimination from the respiratory tract)
* Mainly due to the breakage of the disulphide bonds in the new mucoproteins
Therapeutic Uses:
* Respiratory infections e.g. bronchitis
* Cystic fibrosis
* Asthma
Expectorant = promotes the secretion of sputum

Question 9

Function:
Insulin resistance

Answer 9

Functions:
* Increases insulin sensitivity (Antioxidant)
Therapeutic Uses:
* Diabetes mellitus
* PCOS

Question 10

Other Therapeutic Uses

Answer 10

• HIV support: Associated with increased glutathione, reduced oxidative stress and enhanced T-cell count and activity
• Neuro-degenerative diseases e.g. Parkinson, Alzheimer’s (oxidative stress)

Question 11

Other applications

Answer 11

• In emergency medicine, NAC is used as an antidote for paracetamol toxicity resulting from an overdose (as paracetamol is detoxified using the glutathione pathway) – protecting the liver from damage.

Question 12

Dosage

Answer 12

• 600mg - 1.5g/day (e.g. 600mg x 2 per day).

Question 13

Drug Interactions

Answer 13

• Nitro-glycerine (can cause hypotension and headaches).
• Caution also with insulin use (improves receptor abilities to pick up insulin)

Question 14

Caution

Answer 14

• Can cause GI adverse effects (stimulates liver into action, bile, detox etc)