Enzyme polymorphism is the occurrence of inherited variation in enzyme structure, abundance, or activity within a population. Alternative alleles can encode molecular forms with different biochemical properties or alter the amount of enzyme produced [1]. Such genetic variation contributes to differences in metabolic phenotypes among individuals [2]. In methyltransferases, sequence variation can change enzyme properties and the rate at which particular compounds undergo methylation [3]. Regulatory variants, coding substitutions, and differences in gene copy number can contribute through distinct molecular routes. The observed phenotype also incorporates the cellular environment and the substrate being examined [4]. Characterization links the frequency and identity of inherited variants to measurements of expression or catalytic function, while distinguishing variants with demonstrated functional effects from those without established biochemical consequences [5].