Quick question about classic galactosaemia

[Phloston]

From a source:

"A 5-day old newborn with poor prenatal care is admitted with sepsis. The causative organism is identified as Escherichia coli. The mother tells you that the baby had never "had a good appetite", and you note that the neonate is both jaundiced and has a distended abdomen with a fluid wave. Which test should be ordered?"

Answer: Red blood cell galactose-1-phosphate uridyltransferase levels

Firstly, I had not been aware that E. coli sepsis occurs with classic galactosaemia. I searched Google, and sure enough, it's there. Maybe that's already obvious to some people, but it's not in FA, and this was a wtf-question for me (aside from the hepatic findings, which make sense).

My actual question though is that the answer is red blood cell galactose-1-phosphate uridyltransferase levels. For some reason, I had assumed that this enzyme was found in the liver, not in RBCs. Could someone help out here?

Cheers,

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[teenmachinery1]

From a source:

"A 5-day old newborn with poor prenatal care is admitted with sepsis. The causative organism is identified as Escherichia coli. The mother tells you that the baby had never "had a good appetite", and you note that the neonate is both jaundiced and has a distended abdomen with a fluid wave. Which test should be ordered?"

Answer: Red blood cell galactose-1-phosphate uridyltransferase levels

Firstly, I had not been aware that E. coli sepsis occurs with classic galactosaemia. I searched Google, and sure enough, it's there. Maybe that's already obvious to some people, but it's not in FA, and this was a wtf-question for me (aside from the hepatic findings, which make sense).

My actual question though is that the answer is red blood cell galactose-1-phosphate uridyltransferase levels. For some reason, I had assumed that this enzyme was found in the liver, not in RBCs. Could someone help out here?

Cheers,

I think GALT is in most if not all tissues. You're probably associating it with the liver because it's a site for major pathology.

 

[ipizzy]

A quick google search shows papers detailing measurement of the enzyme from RBCs as a method of diagnosis. I would just assume levels are measured from RBCs because blood samples are easier and cheaper to obtain than liver biopsies. I agree it's easy to classify all metabolism enzymes as belonging to the liver but many of these enzymes are elsewhere too! In terms of why this enzyme is expressed by RBCs in particular, I'm not sure. But anoter quick google search yielded that while RBCs mainly use glucose, they can also use galactose, fructose, and mannose. RBCs also have minimal glycogen stores and express the enzymes involved in glycogen metabolism, but the activity of glycogen synthase is relatively low. (From Storey's Functional Metabolism: Regulation and Adaptation). So there is clearly some sugar manipulation going on in RBCs (which makes sense since RBCs stick modified sugars on their membranes, as in ABO etc).

 

[Phloston]

A quick google search shows papers detailing measurement of the enzyme from RBCs as a method of diagnosis. I would just assume levels are measured from RBCs because blood samples are easier and cheaper to obtain than liver biopsies. I agree it's easy to classify all metabolism enzymes as belonging to the liver but many of these enzymes are elsewhere too! In terms of why this enzyme is expressed by RBCs in particular, I'm not sure. But anoter quick google search yielded that while RBCs mainly use glucose, they can also use galactose, fructose, and mannose. RBCs also have minimal glycogen stores and express the enzymes involved in glycogen metabolism, but the activity of glycogen synthase is relatively low. (From Storey's Functional Metabolism: Regulation and Adaptation). So there is clearly some sugar manipulation going on in RBCs (which makes sense since RBCs stick modified sugars on their membranes, as in ABO etc).

Thanks for that.

 

[futuredoctor10]

Interesting discussion and question.

What source is the Q from out of curiosity?

 

[Phloston]

Interesting discussion and question.

What source is the Q from out of curiosity?

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