Alkaline phosphatase Q

[Owlie]

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In my chapter about osseous tissue, in the section on intramembranous ossification, my A&P text briefly mentioned alkaline phosphatase being used in the enzymatic reactions relating to the crystallization of osteoid.

I attempted a little bit of research, and skimmed a journal article. From what I understand, alkaline phosphatase hydrolyses phosphate from a bound molecule.

Is this correct?

If so, does it allow for phosphate to be used (by releasing it) in making calcium-phosphate, which is then used in conjunction with calcium-hydroxide to make hydroxyapatite?

Is alkaline phosphatase (AP) then only able to hydrolyze phosphate from in specific forms so as not to release it from its bond with calcium? I feel like, from reading, that it was explained that AP hydrolyses phosphate, so that means it shouldn't be able to break apart a calcium/phosphate bond.



Maybe this is a completely obvious, or ridiculous question, but I'm curious!

 

[CaptainSSO]

I don't really know about how it pertains to intramembranous ossification, but you're correct--alkaline phosphatase has to hydrolyze phosphate from organic molecules. Hydroxyapatite is Ca10(OH)2(PO4)6 (somehow I remember that from the MCAT), which is just a salt, an electrostatic bond rather than a covalent one, so there is nothing for alkaline phosphatase to hydrolyze.

Edit: That applies to any phosphatase--they won't affect phosphate salts.

That's a little deep for med school purposes, though. For your future studies, you'll mainly just want to know that alkaline phosphatase is found in hepatic cells lining the bile canaliculi in the liver, and increased serum levels along with conjugated bilirubin would typically indicate a biliary obstruction as opposed to hepatocyte necrosis/apoptosis. There's some other conditions it's associated with but that's probably the big one you need to have memorized.

 

[Owlie]

I don't really know about how it pertains to intramembranous ossification, but you're correct--alkaline phosphatase has to hydrolyze phosphate from organic molecules. Hydroxyapatite is Ca10(OH)2(PO4)6 (somehow I remember that from the MCAT), which is just a salt, an electrostatic bond rather than a covalent one, so there is nothing for alkaline phosphatase to hydrolyze.

Edit: That applies to any phosphatase--they won't affect phosphate salts.

That's a little deep for med school purposes, though. For your future studies, you'll mainly just want to know that alkaline phosphatase is found in hepatic cells lining the bile canaliculi in the liver, and increased serum levels along with conjugated bilirubin would typically indicate a biliary obstruction as opposed to hepatocyte necrosis/apoptosis. There's some other conditions it's associated with but that's probably the big one you need to have memorized.

Thank you! 🙂

 

[GoSpursGo]

Moving to pre-allo

 

[deleted329605]

In my chapter about osseous tissue, in the section on intramembranous ossification, my A&P text briefly mentioned alkaline phosphatase being used in the enzymatic reactions relating to the crystallization of osteoid.

I attempted a little bit of research, and skimmed a journal article. From what I understand, alkaline phosphatase hydrolyses phosphate from a bound molecule.

Is this correct?

If so, does it allow for phosphate to be used (by releasing it) in making calcium-phosphate, which is then used in conjunction with calcium-hydroxide to make hydroxyapatite?

Is alkaline phosphatase (AP) then only able to hydrolyze phosphate from in specific forms so as not to release it from its bond with calcium? I feel like, from reading, that it was explained that AP hydrolyses phosphate, so that means it shouldn't be able to break apart a calcium/phosphate bond.



Maybe this is a completely obvious, or ridiculous question, but I'm curious!

When you consider the sheer magnitude of ions like PO4 in a cell, I highly doubt that a phosphatase would be required to provide an ion reagent to form hydroxyapatite. Simply, it just removes an inorganic phosphate from some molecule in the cell. If I had to guess, this would probably be a protein.

I think you would need more info to figure out how specifically this phosphatase helps form hydroxyapatite. I am assuming that for such a process, multiple steps would be required for the final product. One way the phosphatase could help regulate the pathway is by leading to the activation/inactivation of whatever protein has the phosphate being removed from. This could even be a group of proteins that all have their phosphate groups removed when the activation of this phosphatase occurs. I think less likely, you would have the energy releasd by the cleavage of the inorganic phosphate being used to drive the formation of hydroxyapatite (at this point, although maybe that occurs later down the pathway).

So yea, phosphatases are regulatory enzymes, and they are a type of enzyme that can amplify secondary messanger effects.

 

[Owlie]

When you consider the sheer magnitude of ions like PO4 in a cell, I highly doubt that a phosphatase would be required to provide an ion reagent to form hydroxyapatite. Simply, it just removes an inorganic phosphate from some molecule in the cell. If I had to guess, this would probably be a protein.

I think you would need more info to figure out how specifically this phosphatase helps form hydroxyapatite. I am assuming that for such a process, multiple steps would be required for the final product. One way the phosphatase could help regulate the pathway is by leading to the activation/inactivation of whatever protein has the phosphate being removed from. This could even be a group of proteins that all have their phosphate groups removed when the activation of this phosphatase occurs. I think less likely, you would have the energy releasd by the cleavage of the inorganic phosphate being used to drive the formation of hydroxyapatite (at this point, although maybe that occurs later down the pathway).

So yea, phosphatases are regulatory enzymes, and they are a type of enzyme that can amplify secondary messanger effects.

Well I did read that osteoblasts cause the deposition of calcium salts by raising the amount of local calcium salt concentration above its solubility limit.

 

[deleted329605]

Well I did read that osteoblasts cause the deposition of calcium salts by raising the amount of local calcium salt concentration above its solubility limit.

I'm not sure this is entirely relevent though. DIfferent salt (Ca vs. PO4), different area in the body (I'm assuming that the phosphatase you mentioned functions within cells, whereas the deposition of Ca occurs in the intercellular region).

 

[Owlie]

I'm not sure this is entirely relevent though. DIfferent salt (Ca vs. PO4), different area in the body (I'm assuming that the phosphatase you mentioned functions within cells, whereas the deposition of Ca occurs in the intercellular region).

It's the same area of the body as the osteoblasts. The place where it was mentioned (AP) was in intramembranous ossification where osteoid secreted by mesenchymal cells is calcified after they differentiate into osteoblasts. There's no reason AP must be an intracellular enzyme; perhaps it isn't - perhaps it is. I haven't read that yet. It seems to me that they would be extracellular.

 

[487806]

Moving to pre-allo

I actually thought this was a medical school type question. Thanks for proving me wrong. 👍

Wow, so I only study physio until med school.

Back to point, OP, I believe you got your concepts down correctly.

 

[Owlie]

I actually thought this was a medical school type question. Thanks for proving me wrong. 👍

Wow, so I only study physio until med school.

Back to point, OP, I believe you got your concepts down correctly.

I put it in the allo forum cause I thought the med students would know a bit more about these processes. *shrug* oh well

Thanks. It helped a lot to have a conversation about it to flesh out my ideas. Thinking to myself can sometimes lead to logical inconsistencies.

 

[487806]

I put it in the allo forum cause I thought the med students would know a bit more about these processes. *shrug* oh well

Thanks. It helped a lot to have a conversation about it to flesh out my ideas. Thinking to myself can sometimes lead to logical inconsistencies.

I agree that med students would know the answer better... I don't know. Probably mentioning A&P gave away.