Glycosidic Linkages & Sialic Acids etc

Question 1

What are sialic acids

Answer 1

Acyl-derivates of neuraminic acid

Question 2

Neuraminidase

Answer 2

Also called sialidase

Cleaves glycosidic linked sialic acids

This reaction is associates with Influenza (H1N1)

Question 3

What are the 3 main sialic acids

Answer 3

N-glycolylneuraminic acid (Neu5Gc)

N-acetylneuraminic acid (NeuAc or Neu5Ac)

N-acetyl-4-O-acetylneuraminic acid

Question 4

Glycosidic linkage

Answer 4

OH group at C1 —> OH group at C4

H20 is release

Question 5

Lactose linkage

Answer 5

C1 OH of Beta-D-galactopyranose

+

C4 OH of D-glucopyranose

—> beta-1,4-galactosidic linkage

Question 6

The synthesis of a glycosidic linkage requires what 3 things

Answer 6

1. Nucleotide sugar donor
2. Sugar acceptor
3. Glycosyltransferase

Question 7

Major nucleotide sugar donors =

Answer 7

UDP donors (-Gal, -Glc, -GlcA, -GalNAc, and GlcNAc…..NO Mannose)

GDP donors (-Man, -Fuc)

CMP donors (-N-acetylneuraminic acid, -N-glycolylneuraminic acid….aka sialic acid donors)

Question 8

Where in cell are sugar chains made

Answer 8

ER and Golgi

Question 9

Making lactose in mammary gland

Answer 9

In lactose = alpha-lactalbumin (sugar acceptor modifier)

So UDP-Gal + Glu —(beta-galactotransferase)—>lactose

Question 10

Making ‘lactose’ not in mammary gland

Answer 10

Alpha-lactalbumin is NOT present

So acceptor = N-acetylglucosamine

Product = N-acetyllactosamine

Question 11

Enzyme that cleaves glycosidic linkages

Answer 11

Glycosidases

Lactose = beta-galactosidase