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Health Dictionary

Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.

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Transcobalamin

Introduction

Transcobalamins are carrier proteins which bind cobalamin (B12).

Types

Types

  • Transcobalamin I (TCN1), also known as haptocorrin, R-factor, and R-protein, is a glycoprotein produced by the salivary glands of the mouth. It primarily serves to protect cobalamin (Vitamin B12) from acid degradation in the stomach by producing a Haptocorrin-Vitamin B12 complex. Once the complex has traveled to the more neutral duodenum, pancreatic proteases degrade haptocorrin, releasing free cobalamin, which now binds to intrinsic factor for absorption by ileal enterocytes.
  • Transcobalamin II (TCN2) binds cobalamin once it has been taken up by enterocytes of the terminal ileum and the “Intrinsic Factor-Vitamin B12” complex has been degraded. The TCII-Vit B12 complex then is processed in the liver.
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