Haptocorrin

What are the other names of Haptocorrin?

Haptocorrin also known as

• Transcobalamin-1
• Cobalophilin
• R-Protein
• R-Factor

What is the Essential function of haptocorrin?

Function of haptocorrin - protection of the acid-sensitive vitamin B12 while it moves through the stomach.

What is the structure of haptocorrin?

• It is a glycoprotein

How the haptocorrin is secreted?

•   Produced by -salivary glands
• Produced in response to ingestion of food

What is the mechanism of action of haptocorrin?

Vitamin B12 is sensitive to the HCl in the gastric secretions

Vitamin B12 attaches haptocorrin, which has a high affinity for its molecular structure

Vitamin B12 and haptocorrin create a complex

Haptocorrin–B12 complex is resistant to  acid and reaches duodenum.

In the duodenum pancreatic proteases cleave haptocorrin, releasing vitamin B12 in its free form.

Parietal cells in stomach produce intrinsic factor (IF), which binds the B12 after its release from haptocorrin by digestion

Vitamin B12 attaches to the intrinsic factor (IF) in duodenum to create a vitamin B12–IF complex. This complex then reaches ileum.

Cubilin receptors in ileum absorbs B12–IF complexes.

Cobalamin-IF complex enters the ileal cell,

IF is destroyed

Cobalamin appears in portal blood attached to transcobalamin (TC) II - After a delay of about 6 h

Which receptors in ileum helps absorption of Vitamin –B12 and IF Complex?

Cubilin receptors present in ileum identify the B12–IF complexes and absorb into the circulation by endocytosis-mediated absorption.

Why oral replacement with large vitamin B-12 doses is appropriate for Pernicious anemia?

Cobalamin requires IF for absorption - 99%.

Free cobalamin is absorbed passively in the terminal ileum -1%.

This why oral replacement with large vitamin is required in pernicious anemia