Burst kinetics is a form of enzyme kinetics that refers to an initial high velocity of enzymatic turnover when adding enzyme to substrate. This initial period of high velocity product formation is referred to as the "Burst Phase". This period is observed as the enzymes become saturated with substrate up until all enzymes are saturated. Once all enzymes are saturated, the Burst Phase gives way to a linear reaction velocity. An example of a burst kinetics is observed in Step 6 of Glycolysis involving GAP Dehydrogenase (GAPDH) and the reduction of NAD+ to NADH. Furthermore, the production of NADH can be measured as it is yellow and absorbs at 340 nm.