D-Mannose: More than just a sugar?
Sugar doesn't exactly have the best reputation. Too much of it is said to be bad for your teeth, make you fat and generally promote an unhealthy diet. This may be true for common household sugar, which is consumed all too generously in all foods. But the world of sugar is much more diverse; some of the most important building blocks of life come from it. The example of D-mannose shows just how different the functions of sugar can be.
D-mannose – a sugar building block
D-mannose is a simple sugar, i.e. a single sugar building block. A quick look at the chemistry: Simple sugars consist of a carbon chain that is between two and nine carbon atoms long. They also contain at least one carbonyl group and one hydroxy group. The hydroxy groups - consisting of an oxygen atom (O) and a hydrogen atom (H), hence also called OH group - can be arranged in different spatial positions along this chain. If you imagine the chain as linear, the OH groups can be on the left or right of the chain. If the OH group that is furthest from the center of the molecule is on the left side, it is called L configuration. If it is on the right side, it is in D configuration. Mannose, like most other sugars, only occurs naturally in the D configuration. The L form can be produced synthetically, but plays no role in nature. When we talk about mannose, we therefore usually mean D-mannose. One of the properties of sugars is that they can occur both as a chain and in the form of a ring structure. Together with their binding ability, this means that they can serve as building blocks for very complex molecules.
Simple sugars and complex sugars – why are they so important?
Monosaccharides such as mannose can easily combine with one another and are then referred to as multiple sugars or polysaccharides. Glucose and fructose - also known as grape sugar and fruit sugar - are typical simple sugars. When they are combined, they form the double sugar sucrose, our household sugar. Glucose is the most important energy supplier for all animal life and - another word for the different sugars - the most common carbohydrate. Glucose is also the basis for cellulose, the most important component of all plant cell walls and the most common polysaccharide. Different sugar building blocks can also be found in animal cell walls. Sugar is therefore not only an energy supplier and a fattening agent, but also an important building block of life. Depending on their appearance, the different types of sugar are also metabolized differently. We humans cannot do much with cellulose. Starch, on the other hand, also a polysaccharide made of glucose building blocks, goes straight to your hips.
Mannose as a sugar substitute
This brings us back to mannose. This is almost identical to glucose, although it is mirrored in some places. These differences are enough for mannose to still taste sweet - it is almost 60 percent as sweet as glucose - but is mostly excreted through the intestines and urine. Mannose is therefore even suitable as a sugar substitute for diabetics.
Importance of mannose as a glycoprotein in the cell wall
The human body is able to produce mannose and other simple sugars from glucose or fructose. This is necessary because monosaccharides play an important role in the construction of the outer cell walls. There they bind to proteins and form so-called glycoproteins and also glycolipids (Greek, glykos = sweet). This outermost layer of the cells is also called the glycocalyx. It protects the cell from drying out, keeps foreign bodies away and prevents self-digestion in the intestinal epithelium. Due to its ability to bind water, the glycocalyx is able to form a layer of mucus. This is particularly important in the intestinal epithelium and the urothelium of the bladder. There, an intact layer of mucus is involved in the defense against bacteria, for example. The glycocalyx is also in contact with the antibodies of the immune system and thus helps to recognize foreign substances. In addition, the composition of the glycocalyx varies from person to person. This is reflected in the blood group, among other things. This is determined by the nature of the glycocalyx of the red blood cells.
The chemical structure of D-mannose and L-mannose.
Sugar in Current Research
Due to the different influences of the various sugar building blocks on our lives, an entire branch of research called glycobiology has developed in recent years that deals with the complex biochemical processes of saccharides. Exciting findings about the cellular and molecular biological processes of our body can be expected from this still young field of research in the future. We would therefore like to encourage you to delve deeper into this topic. The Internet offers extensive information on a simple sugar such as D-mannose alone.
