From direct mutation, alterations

Malmberg A, Strange PG. Site-directed mutations in the third intracellular loop of the serotonin 5-HT1A receptor alter G protein coupling from Gj to Gs in a ligand-dependent manner. J Neurochem 2000 75 1283-1293. 

Novo, C., Farnaud, S., Tata, R., et al. 2002. Support for a three-dimensional structure predicting a Cys-Glu-Lys catalytic triad for Pseudomonas aeruginosa amidase comes from site-directed mutagenesis and mutations altering substrate specificity. Biochemistry Journal, 365 731-8. 

While many diseases have long been known to result from alterations in an individual s DNA, tools for the detection of genetic mutations have only recently become widely available. These techniques rely upon the catalytic efficiency and specificity of enzyme catalysts. For example, the polymerase chain reaction (PCR) relies upon the ability of enzymes to serve as catalytic amplifiers to analyze the DNA present in biologic and forensic samples. In the PCR technique, a thermostable DNA polymerase, directed by appropriate oligonucleotide primers, produces thousands of copies of a sample of DNA that was present initially at levels too low for direct detection. 

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