**Core Concept**
The question is testing the knowledge of a specific enzyme involved in the metabolism of glycine in the liver mitochondria. Glycine metabolism is crucial in the synthesis of porphyrins, creatine, and glutathione, among other important molecules.

**Why the Correct Answer is Right**
The correct answer involves the enzyme glycine cleavage enzyme (also known as glycine decarboxylase), which is a mitochondrial enzyme responsible for the cleavage of glycine into ammonia, carbon dioxide, and a single carbon unit (5,10-methylene-tetrahydrofolate). This reaction is essential for the metabolism of glycine and the synthesis of other important biomolecules. The glycine cleavage enzyme is a multi-enzyme complex that consists of four different subunits, each with a distinct function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the enzyme involved in glycine cleavage in liver mitochondria.
**Option B:** This option is also incorrect because it is not the enzyme responsible for the cleavage of glycine.
**Option C:** This option is incorrect because it is not related to glycine metabolism in liver mitochondria.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the glycine cleavage enzyme is a mitochondrial enzyme, and its dysfunction can lead to various clinical disorders, including nonketotic hyperglycinemia, a rare genetic disorder characterized by elevated levels of glycine in the blood and urine.

**Correct Answer: C. Glycine decarboxylase**