In the bloodstream, another protein, transcobalamin2 carries the Vitamin B12 to all the cells in the body, transporting any extra to the liver for storage.
Adenosylcobalamin is also an "active" B12 form, making this coenzyme immediately available for use by the body. It is required for an enzyme known as MCM (Methylmalonyl Coenzyme A Mutase), which resides in the mitochondria and is needed to make succinyl CoA to produce energy in the citric acid cycle. In humans, Adenosylcobalamin is found mainly in the tissues especially the liver. It is the primary form of B12 found in non-human animals.
Deficiency of Vitamin B12
There is no one particular symptom that suggests a B12 deficiency. Symptoms may depend on the age and genetic disposition of the individual, and also the length and severity of deficiency. Because Vitamin B12 has so many functions, including the health of nerves, brain, blood and immune system, as well as the formation of DNA, B12 deficiency can impair functioning in almost any part of the body. The following signs and symptoms are common symptoms of B12 deficiency but can also arise from other causes.
Mental changes include irritability, apathy, sleepiness, paranoia, personality changes, depression, memory loss, dementia, hallucinations, violent behaviour and in children developmental delay and/or autistic behavior. Neurological signs and symptoms include pain, tingling or numbness, decreased sense of touch, pain or temperature, weakness, loss of awareness of body position, clumsiness, tremor, symptoms mimicking Parkinson’s disease or multiple sclerosis, spastic muscles, incontinence, paralysis, visual changes and damage to the optic nerve. Vascular changes include, transient ischaemic attacks (TIAs or mini strokes), CVA or stroke, coronary artery disease, heart attack, congestive heart failure,
palpitations, low blood pressure when standing causing fainting, deep vein thrombosis (blood clot in the arm or leg) and pulmonary embolism.
Other signs and symptoms may include shortness of breath, generalised weakness, chronic fatigue or tiredness, loss of appetite and weight loss, epigastric pain (poor digestion, full or bloated feeling after eating normal or small meals), diarrhoea or constipation, increased susceptibility to infection, poor wound healing, failure of new born to thrive, tinnitus, vitiligo (white patches of skin), or hyperpigmentation, premature grey hair and impotence.Anybody at any age can become deficient but people may be at an increased risk if they are: