Fundamentals of Diagnostic Enzymology [antikvár]

Enzymes are proteins. They catalyse chemical reactions which would not take place (or would take place only very slowly) without their presence. They can be isolated and sometimes crystallized like other proteins and are also de-natured by heat. They are inactivated by micro-organisms and are sensitive to heavy metals, detergents, changes of pH and ionic strength. Enzymes may exist in forms which catalyse the same chemical reaction but which differ in their physico-chemical properties. These are known as isoenzymes. They may be separated by physical methods (e.g. electrophoresis, chromatography) and also by chemical means. Human lactate dehydrogenase (LDH) can serve as an example. It can be separated by electrophoresis into five fractions, and these isoenzymes all catalyse the same reaction: the conversion of pyruvate to lactate. Different organs contain characteristic proportions of the different LDH isoenzymes. LDH isoenzyme composition may therefore serve as a means of organ identification.