Vitamin B12 Metabolism: A Network of Multi-Protein Mediated Processes

The water-soluble vitamin - vitamin B12, also known as cobalamin, plays a crucial role in cellular metabolism, particularly in DNA synthesis, methylation, and mitochondrial functionality. Its de-ficiency can lead to hematological and neurological disorders, however the manifestation of these clinical outcomes is relatively late. It leads to difficulties in its early diagnosis, often resulting in the development of hidden subclinical cobalamin deficiency. Prolonged lack of vitamin B12 con-dition may have severe consequences including increased morbidity to neurological and cardio-vascular diseases. Beyond inadequate dietary intake, vitamin B12 deficiency might be caused by insufficient bioavailability, blood transport disruptions, or impaired cellular uptake and metabo-lism. Despite nearly 70 years of knowledge since its isolation and characterization, there are still gaps in understanding its metabolic pathways. Thus, this review aims to gather current knowledge about the crucial proteins necessary to efficiently process vitamin B12 in humans, presenting it as a multi-protein mediated network. Based on these findings, we also highlight new potential methods for supporting the evaluation of the risk of epidemiological consequences of vitamin B12 deficiency or clinical warnings of increased risk of vitamin B12 deficiency based on already testing targeting specific moonlighting proteins engaged in vitamin B12 metabolic path-ways.