Even though many therapeutic proteins require only 95% purity, the final product is often tested for microscopic amounts
In biochemistry, enzyme catalysis and lipid structure dictates that substrate affinity, transition state stabilization and phospholipid composition govern function. Therefore Critical impurity is correct as it reflects catalytic efficiency and membrane organization, supported by mechanistic studies and conserved across related systems.
Ref: Berg et al., Biochemistry, 9th Edition, Chapter 13, Metabolism and Bioenergetics, covers glycolysis, citric acid cycle, oxidative phosphorylation and NADH-linked reactions detailing biochemical principles.
