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The three most common disaccharides (sucrose, maltose, and lactose) all contain at least one glucose monomer (sucrose=glucose+fructose, maltose=glucose+glucose, lactose=glucose+galactose), and the vast majority of other disaccharides also contain at least one glucose.

The only outliers to this that I have found are xylobiose (xylose+xylose), rutinulose (rhamnose+fructose), melibulose (galactose+fructose), lactulose (galactose+fructose), and mannobiose (mannose+mannose), and these all seem to be relatively niche/uncommon. Glucose is also one of the only monosaccharides I can find that binds with itself to form a disaccharide, and I have not found any examples of a fructose+fructose or galactose+galactose disaccharide.

What property of glucose makes it so that glucose found in (and is so integral to) so many disaccharides instead of a different monosaccharide, such as fructose or galactose, and why is it able to commonly form a bond with itself, unlike fructose or galactose?

(link to wikipedia article containing list of disaccharides with the monosaccharides they are composed of: https://en.wikipedia.org/wiki/Disaccharide)

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What property of glucose makes it so that glucose found in (and is so integral to) so many disaccharides instead of a different monosaccharide, such as fructose or galactose, and why is it able to commonly form a bond with itself, unlike fructose or galactose?

Some readers seem absorbed with the notion that glucose can "form a bond with itself, unlike" other monosaccharides. This hasn't been addressed because it's an incorrect premise. To my knowledge this happens in many hemiacetals/hemiketals in water.

Glucose is a fundamental hexose; the metabolism of glycolysis is truly central to cellular life. This explains why it's so pervasive, in disaccharides or other carbohydrates. To use the wording of the question, the property of glucose that it explains its pervasive representation in disaccharides is its metabolic availability.

So why is glucose metabolism conserved across all three Domains of life? I explore two reasons.

  1. Glucose metabolism could be central because of evolutionary history. Another type of aqueous biochemistry could prevail under terrestrial chemistries. So galactose-based terrestrial biochemistry is equally possible, in which case it would be overrepresented in biomolecules instead of glucose.

  2. The aqueous abiotic (organic) chemistry of carbon (under terrestrial conditions) support glycolysis as a central metabolic pathway. So a galactose-based terrestrial biochemistry is thermodynamically disfavored.

(Same arguments go for pentose phosphate and TCA cycles, and the few other pathways that are so close to energetic equilibrium as to be amphibolic and metabolically central.)

Evolutionary biology provides evidence for explanation (1). This is because all domains of life share conserved enzymatic machinery for glycolysis; "The phylogenetic distribution of the enzymes of the glycolytic pathway confirms that it is indeed an ancient metabolic pathway, and was present (at least in part) when eukaryotes and prokaryotes diverged about 1800 million years ago."From this reference, p. 224

There are also strong arguments for explanation (2). Below is one article detailing how glycolysis could very plausibly preceed cellular life. Glucose would then be pervasive, in part, because it's a pervasively metabolically-accessible (and chemically stable) sugar, under terrestrial conditions.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4023395/

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  • $\begingroup$ "Evolutionary biology provides evidence for explanation (1)." Can you provide a link to support this (completely reasonable) statement? Thanks. $\endgroup$ Apr 25, 2023 at 23:09
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    $\begingroup$ Your answer makes no connection between the composition of disaccharides and glycolysis, indeed disaccharides are not even mentioned. $\endgroup$
    – David
    Apr 26, 2023 at 8:36
  • $\begingroup$ @Ryan. Perhaps this is a question of stereochemistry. Ask a chemist. $\endgroup$
    – jeremiah
    Apr 28, 2023 at 19:06
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    $\begingroup$ Aren't you putting the cart before the horse? The question isn't "why is glycolysis universal?" $\endgroup$ May 16, 2023 at 17:09
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    $\begingroup$ @Ryan But the question is about disaccharides! The word “glycolysis” doesn’t even appear in the title. I $\endgroup$
    – David
    May 16, 2023 at 18:36
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Part of the explanation for this preponderance in disacharides is perhaps the dominance of glucose generally, and the clear necessity for it to be stored in organisms. The intuitive explanation for that preponderance, including in polysaccharides generally, likely involves some stereochemical property which distinguishes it from galactose, and broadly speaking, fructose. The following is an excerpt from the 'Wikipedia' article on Glucose itself; which seems a good starting point.

Glucose is the most abundant monosaccharide. Glucose is also the most widely used aldohexose in most living organisms. One possible explanation for this is that glucose has a lower tendency than other aldohexoses to react nonspecifically with the amine groups of proteins. This reaction—glycation—impairs or destroys the function of many proteins (e.g. in glycated hemoglobin). Glucose's low rate of glycation can be attributed to its having a more stable cyclic form compared to other aldohexoses, which means it spends less time than they do in its reactive open-chain form.

The reason for glucose having the most stable cyclic form of all the aldohexoses is that its hydroxy groups (with the exception of the hydroxy group on the anomeric carbon of d-glucose) are in the equatorial position. Presumably, glucose is the most abundant natural monosaccharide because it is less glycated with proteins than other monosaccharides. Another hypothesis is that glucose, being the only d-aldohexose that has all five hydroxy substituents in the equatorial position in the form of β-d-glucose, is more readily accessible to chemical reactions, for example esterification or acetal formation. For this reason, d-glucose is also a highly preferred building block in natural polysaccharides (glycans). Polysaccharides that are composed solely of glucose are termed glucans.

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