AMYLASE mystery--2 attack sites?

J. Jeffrey Wilson Ph.D. jjwilson at
Mon Aug 21 23:38:03 EST 1995

Hi Bruce,
Firstly, is your transmittance following the reduction in turbidity 
(iodine blue colour or ?) of the gelatinized cornstarch solution as it is 
hydrolyzed by the amylase or are you actually measuring formation of glucose
in a colorimetric assay?  How long are you following the reaction?  What 
temperature?  Is it possible that bacterial growth on the glucose is occurring,
causing an increase in turbidity?  Try a plate count or microscopic check 
(1000X oil immersion).  Saliva is a good source of bacteria, as you probably

I have heard of re-polymerization of enzyme hydrolyzed cellulose after 
extensive hydrolysis to glucose, but haven't seen this in starch.

Anyway, some food for thought.

Jeff Wilson

On 18 Aug 1995, BruceRat wrote:

> I am a high school teacher using a homemade spectrophotometer to study the
> kinetics of salivary amylase digestion of cornstarch.  Instead of
> following the classic Michaelis-Menten curve, my data indicates that there
> may be a secondary mode of action, masked at high substrate concentration,
> that becomes apparent as substrate is largely consumed.  It shows up as a
> slow drift upwards in transmittance.  Anyone ever noticed this effect? 
> Any suggestions? References?   
> Puzzled,    Bruce Ratcliffe  (BruceRat at AOL.COM)

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