What are kinetics, and what does "contradictory"/"controversial" labeling mean?

In a perfect world, research to understand how genetic mutations change enzyme expression and/or activity would be solid and reproducible. In fact, very few enzymes fall into this category. Those tend to be enzymes involved in drug metabolism and, even then, often it is synthetic drug metabolites or research molecules being studied not the substrate(s) the enzymes evolved to process. In the simplest of terms, enzyme kinetics are determined in a lab setting as a study of the reaction rate of a chemical process at a given temperature and concentration of the substrate being studied. Lab techniques utilized include high performance liquid chromatography and, more recently, mass spectrophotometry. This research characterizes the reference rates for wild type/most common genes and a stated substrate (usually quoted as a Km value at a given temperature and concentration).When it comes to the study of mutations and how they affect rates of reactions, there is no common gold standard for the method employed. Mutations can effect enzymes many ways: they can increase or decrease the transcription and/or expression of the enzyme made by the protein. In this case, the rate or kinetics of the reaction may be the same as wild type, but there is much less (or more) of the enzyme to do work. In addition to changing transcription rates, mutation can impact mRNA processing, stability or splicing. Another possibility is that the mutation may change the amino acid sequence that affects the active site of the enzyme which can either enhance (speed up) or hinder (slow down) binding of substrate.

Given this range of potential changes, researchers have used many methods to study mutation effects on enzyme activity. These include e coli with recombinant DNA, human cell lines engineered to include the mutation, lab animals breed to have the mutation or measuring the activity of enzyme in patient's cells with the mutation (e.g.: lymphocytes, liver cells) in laboratory setting or even in real life situations. It is generally felt that research involving humans is superior to extrapolation from e coli or other mammalian data, but unfortunately this type of information is lacking for many enzymes.

As for the "contradictory" labeling, this refers to conflicting results in the literature. For example: an in vitro human cell line study of an enzyme clearly resulted in reduced activity, but another group of researchers tried to replicate the study and arrived at a different result. Another example would involve research deemed inappropriate due to poor study design or the research methods used are outdated or otherwise unproven. Moreover, in vitro results may not hold when conducted in vivo, as there are more confounding factors like epigenetics or gene-gene interactions to consider. Unfortunately, science is not a smooth progression forward in intellectual understanding.

As with any research, it is important to put results into context and look for supporting or conflicting evidence in the patient. Take enzymatic information with a grain of salt: enzyme activity is a complex trait determined by many factors.