U01.01.080 Enzyme terminology

Enzyme names often reflect the specific biochemical process they catalyze. Understanding the different types of enzymes and their functions is crucial for the USMLE Step 1 exam. The following are key enzyme descriptors commonly encountered:

Common Enzyme Descriptors

Enzyme Type	Function	Example
Kinase	Transfers a phosphate group from a high-energy molecule (usually ATP) to a substrate	Phosphofructokinase
Phosphorylase	Adds inorganic phosphate onto substrate without using ATP	Glycogen phosphorylase
Phosphatase	Removes a phosphate group from a substrate	Fructose-1,6-bisphosphatase
Dehydrogenase	Catalyzes oxidation-reduction reactions	Pyruvate dehydrogenase
Hydroxylase	Adds a hydroxyl group (−OH) onto substrate	Tyrosine hydroxylase
Carboxylase	Transfers CO2 groups with the help of biotin	Pyruvate carboxylase
Mutase	Relocates a functional group within a molecule	Methylmalonyl-CoA mutase
Synthase/Synthetase	Joins two molecules together using an energy source (e.g., ATP, acetyl-CoA, nucleotide sugar)	ATP synthase, acetyl-CoA synthase

Points to Remember

Kinase and Phosphorylase are involved in adding phosphate groups, but kinases use ATP while phosphorylases do not.
Phosphatase is responsible for removing phosphate groups, and its action is the reverse of kinase.
Dehydrogenases are central to redox reactions, which are essential in metabolic processes.
Hydroxylases are involved in adding hydroxyl groups, often to aromatic rings (like tyrosine).
Carboxylases transfer carbon dioxide (CO2) using biotin as a cofactor.
Mutases shift functional groups within a molecule, which is key in metabolism.
Synthases and Synthetases both join molecules but synthetases require energy input, while synthases may or may not.

Key Takeaways for USMLE Step 1

Be able to distinguish between enzymes that transfer groups (e.g., kinase, phosphorylase) and those that remove or relocate them (e.g., phosphatase, mutase).
Understand the role of cofactors like ATP, biotin, and nucleotide sugars in the function of different enzymes.
Familiarize yourself with common enzyme examples and their associated metabolic pathways.

USMLE Step 1 Review Series

Curriculum

U01.01.080 Enzyme terminology

Common Enzyme Descriptors

Points to Remember

Key Takeaways for USMLE Step 1

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