So we have everything pretty much laid out for you already OP but I'll rehash a little bit and consolidate.
Typically you are looking at a 3 step conversion process to turn grain starch into fermentable sugars.
Gelatinization – Process of solubilizing starch granules in water. Typically accomplished by grinding grain and heating in the presence of water.
Liquefaction – Initial breakdown of solubilized starch. Converts starch into dextrins (random sugars) Saccharification – Final breakdown of dextrins into fermentable sugars.
These have to be done in order or, in some cases, simultaneously. It is not a good idea to try to saccharify liquefied starch, nor is it a good idea to try to liquefy un-gelatinized starch.
Enzymes do not assist gelatinization typically. They are generally used for liquefaction and/or saccharification.
Liquefaction we are talking alpha-amylases. Of which there are thee main temperature ranges (already listed in above posts). The ideal part about using a high temperature alpha-amylase is that simultaneous gelatinization and liquefaction can take place at 80-90 C.
Saccharification we are talking beta-amylases or glucoamylases (every enzyme that has “amylase” in it will work on starch because starch = “amylose”). Beta-amylases are common in brewing (as it is found in malted barley) and will work to produce maltose, glucose, and other unfermentable sugars. Glucoamylases are frequently used by distilleries because it will convert all dextrins (random sugars) into glucose. Additionally glucoamylase has a side 1, 6 activity which will allow further degradation of some sugars that were previously unfermentable.
Beta-Glucanases on the other hand are a hemicellulase that will work to break down a very specific compound found commonly in wheat, barley, rye, and oats called beta-glucan. Beta-glucans can cause viscosity issues and gum up a mash or an immersion heater. This enzyme has little to no effect on starch and sugar conversions/yields.
TL: DR. Alpha-amylase is used for Liquefaction, Glucoamylase is good for Saccharification, and Beta-Glucanase is generally only applicable to rye, wheat, or barley mashes.
Please consult your enzyme provider for specific pH and temperature ranges of individual enzymes.