Thiamin (B1)

Question 1

What is the coenzyme form of Thiamin?

Answer 1

TPP: Thiamin Pyrophostphate

Question 2

How is Thiamin converted to TPP?

Answer 2

Two phosphate groups must be added

Occurs in the liver

Question 3

In what form is Thiamin present in foods and how is it absorbed?

Answer 3

Absorbed actively or passively in the small intestine

It is present in plant foods as free thiamin and as TPP in animal foods

Only free thiamin can be absorbed, so intestinal phosphatases convert TPP back into thiamin for absorption

Question 4

How is thiamin transported through the body?

Answer 4

It is transported by red blood cells as TPP

Question 5

What are the 3 main functions of TPP?

Answer 5

1. Assists the enzymes involved in the metabolism of carbohydrates and BCAAs
   - Transamination of BCAAs results in toxic byproducts
   - ‘Maple Syrup Urine Disease’ occurs if not dealt with
   - TPP is required for branched chain alpha ketoacid-dehydrogenase activity to clear the byproducts
2. Thiamin is needed for the normal functioning of the nervous system
3. Required in decarboxylation reactions
   - in glycolysis: converting pyruvate to acetyl CoA
   - in CAC: converting alpha ketogluterate to succinyl-CoA
   - in forming ribose (DNA/RNA)

Question 6

What occurs in Thiamin deficiency?

Answer 6

Beriberi

• Dry beriberi: nervous and muscular system malfunction and peripheral neuropathy
• Wet beriberi: nervous and muscular system malfunction + cardiovascular (congestive heart failure)

Wernicke-Korsakoff syndrome (cerebral beriberi in alcoholism)

• reduced alcohol absorption due to alcohol
• increased excretion due to alcohol
• reduced conversion to TPP due to alcohol
• poor diet?

Question 7

Which foods contain thiamin agonists?

Answer 7

Containing thiaminase (thiamin destroying enzyme):

• raw fish
• shellfish

Contains compound which oxidises thiamin:

• brussel sprouts
• beets

Question 8

Which foods are good sources of thiamin?

Answer 8

• Sunflower seeds
• Ham
• Pork chops
• Navy beans