Enzyme
Definition
biological catalyst, speed up chemical reaction w/o being altered
lowers the AE (min. energy required to start chemical reaction)
Nature & Function
contain additional nonprotein (carbohydrate, lipids/ phosphate)
complete enzyme (holoenzyme), protein part (apoenzyme), nonprotein (cofactor)
proteins with catalytic
substrate = compound being converted in an enzymic reaction
Enzymatic Reactions
combines with a specific substrate to a form an enzymesubstrate complex in a lock & key concept
range pH of 4.5 - 8.0
optimum pH : amylase (4.8), invertase (5.0), pancreatic a-amylase (6.9)
broader optimum range: pectin methylesterase (6.5 to 8.0)
optimum at very high/low: pepsin (1.8), arginase (10.0)
temp. > 40°C, decrease due to denaturation
Properties
Ripening.
food spoilage (rotting).
changes in flavor, color, texture and nutritional
inactivated by heat to extend storage stability of foods
fermentation purposes
extracted & purified to a high degree
Classes
Oxidoreductases
Transferases
Hydrolases
Isomerases (involved in the catalysis isomerizations within one molecule)
Lyases (cleave C−C, C−O, C−N, by elimination/ leaving double bonds/adding groups to double bonds)
Ligases (involved in the biosynthesis of a
compound simultaneous hydrolysis pyrophosphate bond in ATP / triphosphate
Application
Proteases - meat tenderizers (bromelin, papain, ficin)
Lipases - flavor in choc. & cheese
Glucose oxidase - prep. of salad dressings
Pectinases - clarification of fruit juices
Carbohydrases - corn syrup from starch, baking industry (amylase)
Lipoxygenase - bleaching of flours
Phenol oxidase - coffee & raisins
Renin - cheese production
Flavorases - restoration & enrichment of flavor by adding enzyme