PENTOSURIA 



267 



According to recent investigations of Neumann, pentose is present in the 

 nuclemic acid of the thymus; hence it follows that the pentose group is an 

 integral constituent of at least some of the nudeinic acids, if not of all 



Of the pentoses which occur in animal nucleins, that of the pancreas has 

 been most minutely investigated. Bang supposed it to be dextro-rotary and 

 Neuberg has lately arrived at the surprising conclusion that the pancreatic 

 pentose is 1-xylose. This latter theory is of great importance as bearing on 

 the origin of pentose m chronic pentosuria. For, if on other grounds we were 

 inclined to believe that the pentose of urine originates from the pancreatic 

 nuclem such an opinion would by this result be proven to be erroneous. It is 

 impossible to understand how xylose could be changed into arabinose. It is 

 true that we have only proven for pancreatic nuclein that its pentose is 1-xylose; 

 the other nucleins have not been investigated in this respect. 



The researches in metabolism by Bial and myself have also made it appear 

 unlikely that pentoses are formed in the pentosuric patient by an imperfect 

 nuclein decomposition, since the metabolism of the pentosuric shows no such 

 increased destruction of nucleins. Neither the excretion of uric acid nor the 

 excretion of phosphoric acid is increased in pentosuria. It also appears to be 

 impossible that the inactive arabinose in pentosuria originates from other 

 nucleins, and not alone from the pancreas nucleins, and we must search else- 

 where for an explanation of the origin of pentose. 



Carl Neuberg has given us important and interesting conclusions in this 

 field. He demonstrated that the 1-xylose which is found in pancreatic nuclein 

 originates from grape sugar; now we have assumed for a long time that glu- 

 cose is partly oxidized from glycuronic acid. If we consider glycuronic acid 

 as pentose carbonic acid, CfilljoOsCOj, it need only give off its carbo-xylose 

 group to produce dextro-rotary 1-xylose. This the organism requires for the 

 construction of nucleins. On the other hand, in his opinion, the r-arabinose, 

 the urinary sugar of pentosuria, originates in a very different manner. 



As is well known, milk sugar is split up in the intestine into dextrose and 

 galactose; a portion of the galactose is certainly utilized for glycogen pro- 

 duction. Another portion enters into cerebrin, for Thierfelder was able to 

 demonstrate the presence in cerebrin of galactose. The galactose contained 

 in cerebrin, however, is dextro-rotary, like the galactose contained in food. 

 But it is very easy to change this d-galactose to its inactive form, and then 

 from the inactive galactose inactive arabinose may readily be produced by 

 oxidation. Carl Neuberg is therefore of the opinion that inactive arabinose 

 originates from derivatives of galactose. How far this view is correct is still 

 uncertain, for the behavior of i-galactose must be tested in the organism of 

 a pentosuric patient. The behavior of the ordinary d-galactose has been stud- 

 ied by Bial and myself, but we were unable to determine an increase of pentose 

 excretion. 



It is evident from these considerations regarding pentosuria that prior 

 to its discovery by E. Salkowski we had but slight understanding of the sugar 

 metabolism of the human organism, and that in pentosuria we are dealing with 

 an anomaly of sugar metabolism which must be assumed to be an independent 

 one. It has nothing in common with diabetes, and is also net to be regarded 



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