Enzymes

Enzymes are proteins that regulate many metabolic pathways of the body by acting as biochemical catalysts, allowing chemical reactions to take place.

The chemical instigators in digestion are called enzymes.  there are enzymes for every chemical process which needs to happen.  Enzymes are the catalysts of the chemical world.

Enzymatic processes are largely carried out intercellularly, however digestive enzymes are the exception.  They are secreted in the digestive tract to bring about hydrolysis of the three food groups extracellularly.

Enzymes are named in two ways;

  • suffix ‘-ase’ and occasionally ‘-psin’
  • secondly the name of the compound that it is trying to hydrolyse as its prefix.  e.g. lipase is an enzyme that breaks down lipids.  All digestive enzymes can be called hydrolase – as they instigate hydrolysis.

Enzymes are protein-based compounds and have a definite shape when linked together.

Each food compound will have a unique enzyme and a fixed chemical structure  will define it.  The enzyme fixes itself perfectly to the food compound like a key in a lockHydrolysis can only occur when two correct compounds meet.

When an atom loses an electron from its orbiting shell the atom acquires a positive electrical charge.

The pH of the body and it’s fluids is measured by the absence or presence of positively charged hydrogen ions.

H+ is a hydrogen atom that has lost an electron and so becomes a positively charged ion called a cation.

Changes in the pH of the digestive tract will reflect a higher or lower concentration of H+ and will be expressed as a number.  For example a pH of 5 is very acidic and means that there is a high concentration of hydrogen ions.

 Specific Enzymes

Carbohydrates are long chains of sugar molecules called ‘saccharide’ compounds:

  • Polysaccharides – such as starches and glycogen
  • Disaccharides such as sucrosetable sugar, lactosemilk,  or maltosemalt sugar
  • Monosaccharides are simple sugars – glucose, fructose and galactose

Polysaccharides are hydrolysed to dissacharides which are hydrolysed into monosaccharides as they undergo chemical digestion.

Amylases are found in saliva and pancreatic juices are the enzymes that catalyze the hydrolysis of polysaccharides to disaccharides.  The enzymes complete the process of the last stage of hydrolysis; sucrase for sucrose, lactase for lactose and maltase for maltose.  These last enzymes are located in the microvilli of the brush border of the intestinal mucosa and here the disaccharides are converted into monosaccharides which are absorbed straight into the blood through the villi.

Proteins

Are twisted complex chains of their building blocks amino acids.  There an be hundreds of these chains in one protein, so the enzymes involved in protein hydrolysis are endless.  they generally come under the heading proteases and ultimately instigate the hydrolysis of proteins into amino acids.

The main proteases are: pepsin in gastric juice

trypsin and chymotrypsin in pancreatic juice and peptidases in the intestinal brush border.

As amino acids bond together by peptide bonds each and every peptide bond must have individualised and specific enzyme to effect hydrolysis.

Complex chains of amino acids forming proteins are hydrolysed into peptides and then hydrolysed again into their absorbable amino acids in the villi, where they are absorbed into the blood via the microscopic capillaries.

Lipids

Are insoluble in water so hydrolysis would be difficult.  The liver produces bile salts and lecithin these both emulsify lipids, breaking them down into small fatty droplets with the bile salt/lecithin surrounding them as a shell.

These droplets are called micelles and present the enzymes with something small enough that they can digest,.

Lecithin is a phospholipid which makes cell membranes and seals off the droplets as if they were cellsBile salts are formed from cholesterol and do much the same thing.

Pancreatic lipases, the main fat digesting enzymes can now enter the digestive function and hydrolyse the fatty droplets into fatty acids, monoglycerides and glycerol droplets.  These are the three chief components of triglycerides – one of the more common lipids.  Phospholipids will be broken down into their respective sub units of lysophosphatide and fatty acids.

The main factors that are necessary for good enzyme function

The pH in the digestive tract affects the complex molecular structure of proteins.  As enzymes are based on protein-based compounds, the incorrect pH will alter their very specific shapes and render them unable to play a part in hydrolysis.

It can be said that enzymes are very pH sensitive.  When people are very toxic, their pH can change and so add to the problems of digestion and absorption.  This will create a viscious cycle of increaed toxicity and inability to digest and absorb efficiently.  A situation that cannot be rectified by the customary prescription of antibiotics.

Enzymes are pH specific to different food groups.  For example amylase, found in saliva requires a neutral to slightly acidic pH environment to initialise the hydrolysis of starch in the mouth.  Its chemical digestion is gradually inactivated by the increasingly acidic gastric juice.  Pepsin requires the high acidity (hydrochloric acid) to be able to hydrolyse pesin – such a high degree of acidity takes place in the stomach.

Rate Law dictates that if too much of a substance is being formed, that formation will be slowed down and reversed in order to maintain homeostasis.

Proenzymes prevent too much of an enzyme being released and from digesting the body itself.  These operate like a key to a caged tiger.

If enzymes are not present, food cannot be digested.

Modern eating habits may comprise 60-70% processed foods, many of which are made up of compounds not found in nature.  In this case they cannot be fully digested as the specific enzyme will not be present.

However the nutrient compounds may be small enough to be absorbed.  At best they will be excreted away.  At worst they may be detoxified by the liver and excreted through various organs.  This may mean that huge quantities of chemicals and foods that are not found in nature are being absorbed by the body and instead ‘dumped’ somewhere in the body.

Also the misuse of drugs is interfering with body chemistry in a way that is not fully understood.

 

 

 

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