Amylase: Chemistry in its Element

Amylase: Chemistry in its Element


The Chemistry in its Element podcast:
Curious tales of chemical compounds This week, Brian Clegg breaks down an
enzyme to make it easier to digest The ‘ase’ ending to ‘amylase’ singles it out
as an enzyme, a complex organic catalyst usually a protein. This naming convention
was begun by French chemists Anselme Payen and Jean-Francois Persoz back in
1833, when they noticed that a newly discovered substance broke down starch
in barley, separating the husk from the seed. They
commented that its ability inspired them to call the substance
diastase ‘qui exprime précisément ce fait.’ The reason diastase expresses
this fact precisely, as they put it, is because it was derived from the Greek
diastasis, meaning separation. This first enzyme to be discovered gave its ‘ase’
ending to the rest, while diastase became a bracket term for a number of
enzymes catalyzing the conversion of starch into sugars, including the subject
of this podcast: amylase. Here, the nature of the separation is
highlighted, as ‘amylum’ is the Latin for starch. This is a seriously chunky
molecule. Visual representations of amylase look like a massive blob or
tangle – it’s a single chain of 496 amino acids, folded up as is typical of a
protein. Spit a drop of saliva onto your finger
and you are looking at a solution containing amylase. Some mammals, humans
included, have amylase in their saliva to help break down foodstuffs – it’s the job
of that amylase to get started on the carbohydrates in starchy foods, splitting
them into component sugars. Technically speaking, your spit contains alpha
amylase, also known as ptyalin. There are three very different major amylase
enzymes, which all break the same kind of bond linking sugars in starches,
impacting different parts of these long-chain molecules. Beta-amylase is
only produced by plants, bacteria and fungi, and is partly responsible for our enthusiasm for fruit: as a fruit ripens,
this enzyme breaks down starch into sugars, increasing the fruit’s sweetness. Gamma-amylase, limited to animals and plants, is produced in animals’ small
intestines, while alpha-amylase turns up in saliva and the pancreas. In total,
nineteen members of the amylase family have been classified, mostly from
microbial sources. The level of amylase in your saliva is likely to differ
depending on regional DNA variation. The gene responsible for the protein
production repeats in our DNA, but in areas with long-term, high-carbohydrate
diets, the repeat occurs more frequently. In Japan, with a history of rice
consumption, for example, there can be more than twice the number of copies of the
gene, and hence more amylase in the saliva, compared with a country with a
low starch diet. Outside the body, amylase is essential for brewing beer, usually in a mix of alpha and beta forms from malt. This is a grain, most often barley, which
is doused in water to allow it to germinate. As the seed starts to grow, it
produces amylase to liberate sugars to nurture the growing plant, but the
amylase is preserved by heating or smoking the sprouting grain. The malt is
then soaked in hot water so the enzymes go to work on the remaining starch –
depending on the temperature, alpha or beta amylase can dominate, leading to a
different mix of sugars, which are then fermented using yeast. Some early
processes for producing alcoholic drinks used amylase from saliva instead of malt.
Here the grain was chewed before spitting it into water to ferment.
Perhaps best known is the beer from South and Central America, usually
produced from maize, known as chica, but the process was historically used
everywhere from Japan in making sake, which despite being called rice wine is
technically a high alcohol beer, to the African millet beer, pombe – though in all
cases malting is now the norm. In the west,
bread and beer were the staple food and drink before modern times. The production
processes of the two are closely related. In each case, amylases break down some
of the starch in processed grains before yeast to convert sugars to alcohol –
though for bread purposes, the alcohol content evaporates during baking and it’s
the by-product of carbon dioxide that’s important to make the bread rise. In
traditional breadmaking, the amylase only comes from yeast, resulting in a
slow process, but flour treatment agents containing amylase are now often added
to speed up the bread production. Alpha-amylase also turns up in
biological detergent. The distinction between ‘bio’ and ‘non-bio’ is the inclusion
of a range of enzymes to break down grease, carbohydrates and more. Amylase, of
course, goes for the starchy stains, such as gravy, chocolate and ice-cream,
breaking parts of large and soluble molecules into soluble sugars. Once humans developed the capability to produce amylase in their saliva, it helped them
get more out of their food – but this was only the start for an enzyme that brings
us our daily bread, an enjoyable glass of beer and even clean clothes.
It may not save lives, but amylase certainly makes life more palatable. That was Brian Clegg with amylase and
next week, it is my turn again and I’ll be celebrating the birthday of a Nobel
laureate – Carl Peter Henrik Dam, who shared the 1943 Prize in medicine for
his role in the discovery of vitamin K. Until then, find all of our previous
podcasts at chemistryworld.com/podcasts and get in touch with any
suggestions – email [email protected] or tweet @chemistryworld.
I’m Ben Valsler, thank you for joining me.