Description
Holotranscobalamin, often referred to as holoTC, is the biologically active fraction of Vitamin B12 (cobalamin) that is bound to a protein called transcobalamin. This complex plays a critical role in the transport of Vitamin B12 within the body.
This form is crucial because it is the only form of Vitamin B12 that can be actively taken up by cells via specific receptors. Once inside the cell, Vitamin B12 is released and can be converted into its active forms, Methylcobalamin and Adenosylcobalamin, which are essential for DNA synthesis, red blood cell production, and neurological function.
Measurement of holotranscobalamin levels in the blood is often used as an early and more specific marker of Vitamin B12 deficiency than total Vitamin B12 levels. This is because holotranscobalamin reflects the amount of B12 that is immediately available for cellular uptake and use.
Testing for holotranscobalamin levels can help diagnose Vitamin B12 deficiency more accurately, especially in cases where traditional total B12 tests might be misleading (e.g., when total B12 levels are normal but holotranscobalamin levels are low, indicating functional deficiency).