Which of the following is involved in 1 carbon metabolism?
**Core Concept**
1-carbon metabolism involves the transfer of one-carbon units, which are essential for the synthesis of nucleic acids, amino acids, and other biomolecules. This process is crucial for various cellular functions, including DNA synthesis, repair, and methylation.
**Why the Correct Answer is Right**
The correct answer involves the enzyme **Carbamoyl Phosphate Synthetase I (CPS I)**, which is a key enzyme in the 1-carbon metabolism pathway. CPS I catalyzes the condensation of ammonia with bicarbonate to form carbamoyl phosphate, a crucial step in the synthesis of citrulline and subsequently arginine. This process is essential for the urea cycle and the synthesis of nucleotides.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **Pyruvate Dehydrogenase (PDH)** is involved in the metabolism of pyruvate to acetyl-CoA, which is a critical step in the citric acid cycle but not directly involved in 1-carbon metabolism.
**Option B:** This option is incorrect because **Glucose-6-Phosphatase** is an enzyme involved in gluconeogenesis and glycogenolysis, playing a role in glucose metabolism but not in 1-carbon metabolism.
**Option C:** This option is incorrect because **Acetyl-CoA Carboxylase (ACC)** is a key enzyme in fatty acid synthesis, catalyzing the carboxylation of acetyl-CoA to malonyl-CoA, which is not directly involved in 1-carbon metabolism.
**Clinical Pearl / High-Yield Fact**
1-carbon metabolism is crucial for the synthesis of purines and pyrimidines, which are essential components of nucleic acids. Deficiencies in enzymes involved in 1-carbon metabolism, such as carbamoyl phosphate synthetase I, can lead to disorders like ornithine transcarbamylase (OTC) deficiency, a urea cycle disorder.
**Correct Answer:** C. Carbamoyl Phosphate Synthetase I (CPS I)