Vitamin required for the activity of transaminases is:
**Core Concept**
Transaminases, also known as aminotransferases, are a group of enzymes that catalyze the transfer of an amino group from an amino acid to a keto acid, playing a crucial role in amino acid metabolism and the synthesis of glucose through gluconeogenesis. These enzymes require a co-factor to facilitate their activity.
**Why the Correct Answer is Right**
The correct answer is Pyridoxine (Vitamin B6), which serves as a co-factor for transaminases. Pyridoxine is essential for the activity of transaminases, such as alanine transaminase (ALT) and aspartate transaminase (AST), by participating in the formation of the enzyme-substrate complex. The vitamin is oxidized to pyridoxal phosphate (PLP), which then binds to the enzyme, enabling the catalytic reaction to occur. The PLP molecule acts as an amino group acceptor, facilitating the transfer of the amino group from the amino acid to the keto acid.
**Why Each Wrong Option is Incorrect**
**Option A:** Riboflavin (Vitamin B2) is not directly involved in the activity of transaminases. While it is essential for energy metabolism and the synthesis of flavin adenine dinucleotide (FAD), it is not the correct answer.
**Option B:** Niacin (Vitamin B3) is crucial for redox reactions and the synthesis of NAD and NADP, but it is not directly involved in the activity of transaminases.
**Option C:** Folic acid (Vitamin B9) is essential for one-carbon metabolism and the synthesis of nucleic acids, but it is not the correct answer.
**Clinical Pearl / High-Yield Fact**
The activity of transaminases is often used as a marker for liver damage or disease. Elevated levels of ALT and AST in the blood can indicate liver cell injury, which can be caused by various factors, including viral hepatitis, alcohol abuse, and drug-induced liver injury.
**Correct Answer:** C. Pyridoxine (Vitamin B6)