Not homework! But can you have PKU and AKU (genetics-related)?

[Jabberwocky12]

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Hey guys,

So I was in genetics today and my teacher was talking about the pathway for PKU and AKU (simplified).

Phenylalanine (converted by Enz in Step A) to Tyrosine (converted by Enz in Step B) to CO2 + H2O.

Obviously there is more to it than that but this is what she was talking about. PKU is when Phenylalanine isn't converted to Tyrosine and AKU is when Tyrosine isn't converted to the final products. We talked about their happlosufficiency and whatnot, which was easy to understand. Now she asked in class specifically that if a person is lacking all enzymes in both Step A and in Step B, what condition would they have and through what mechanism?

Half the class said genetic complementation was the mechanism and the person would have both AKU and PKU. The other half said epistasis and that the person would only have PKU. There were a few here and there that said AKU with epistasis, so I guess less than half of the class answered for the first two 😛.

So the teacher said that the result is only ONE condition, which is PKU. The logic was that if a person couldn't convert phenylalanine to tyrosine in Step A, it doesn't matter if the enzymes in step B don't work.

I feel this is totally false but she says that is correct. Now she IS the genetics teacher but she couldn't explain it in a way to me that would make me believe that AKU couldn't be a result as well, with the answer being both PKU and AKU.

People change diets to work around PKU all the time, and tyrosine could be found in proteins through digestion (such as from meat, I believe.) I'm also confident there has to be another mechanism somewhere that could provide tyrosine since many systems in the body have backups in case of failure. We also talked about determining enzymatic pathways of a compound by various mutations of bacteria, and then introducing various compounds to determine the pathway. (i.e. if A converts to B then to C using enzymes 1,3,2, we would mutate 1,3, and 2 and introduce A, B, and C to see if they survive if C is the final product.) Wouldn't it be significant to have both steps not working? Isn't PKU defined as the inability only of converting phenylalanine to tyrosine?

Opinions? This isn't homework, just me trying to figure out WHY the person wouldn't have both. It seems like in the real world this would be significant, and she is all about real-world application in genetics. I just don't see where her logic is coming from here.

Thoughts would be greatly appreciated, thanks for the input!

 

[R2pharmD2]

Hey guys,

So I was in genetics today and my teacher was talking about the pathway for PKU and AKU (simplified).

Phenylalanine (converted by Enz in Step A) to Tyrosine (converted by Enz in Step B) to CO2 + H2O.

Obviously there is more to it than that but this is what she was talking about. PKU is when Phenylalanine isn't converted to Tyrosine and AKU is when Tyrosine isn't converted to the final products. We talked about their happlosufficiency and whatnot, which was easy to understand. Now she asked in class specifically that if a person is lacking all enzymes in both Step A and in Step B, what condition would they have and through what mechanism?

Half the class said genetic complementation was the mechanism and the person would have both AKU and PKU. The other half said epistasis and that the person would only have PKU. There were a few here and there that said AKU with epistasis, so I guess less than half of the class answered for the first two 😛.

So the teacher said that the result is only ONE condition, which is PKU. The logic was that if a person couldn't convert phenylalanine to tyrosine in Step A, it doesn't matter if the enzymes in step B don't work.

I feel this is totally false but she says that is correct. Now she IS the genetics teacher but she couldn't explain it in a way to me that would make me believe that AKU couldn't be a result as well, with the answer being both PKU and AKU.

People change diets to work around PKU all the time, and tyrosine could be found in proteins through digestion (such as from meat, I believe.) I'm also confident there has to be another mechanism somewhere that could provide tyrosine since many systems in the body have backups in case of failure. We also talked about determining enzymatic pathways of a compound by various mutations of bacteria, and then introducing various compounds to determine the pathway. (i.e. if A converts to B then to C using enzymes 1,3,2, we would mutate 1,3, and 2 and introduce A, B, and C to see if they survive if C is the final product.) Wouldn't it be significant to have both steps not working? Isn't PKU defined as the inability only of converting phenylalanine to tyrosine?

Opinions? This isn't homework, just me trying to figure out WHY the person wouldn't have both. It seems like in the real world this would be significant, and she is all about real-world application in genetics. I just don't see where her logic is coming from here.

Thoughts would be greatly appreciated, thanks for the input!

An interesting question, and I think she may have just oversimplified things. I wiki'd/googled AKU and PKU, and it seems like the symptoms of PKU are much more severe than AKU. Wikipedia says AKU can be asymptomatic while untreated PKU can cause brain damage and so on. Maybe her point was that if you have both, only the PKU is relevant? That's not a terribly satisfactory answer though.

 

[Jabberwocky12]

An interesting question, and I think she may have just oversimplified things. I wiki'd/googled AKU and PKU, and it seems like the symptoms of PKU are much more severe than AKU. Wikipedia says AKU can be asymptomatic while untreated PKU can cause brain damage and so on. Maybe her point was that if you have both, only the PKU is relevant? That's not a terribly satisfactory answer though.

Yeah, my whole thing was on a literal term. Basically, if PKU is defined as X enzymes not working, and AKU is defined as Y enzymes not working, then with X and Y not working either you have both PKU and AKU or some other disease that is defined as both X and Y not working.

Idunno. I kinda want to argue it more with her but she doesn't seem receptive to debate about it. She tends to make these things highlights on tests and whatnot.