#PKU#Inborn error of metabolism#Biochemistry

Added: 2026-05-05

[00:00:00]Hello everyone, I am Moises a second year MBBS student from GMC Sundar. Today I'm going to discuss a very interesting topic that is final ketonia of aromatic amino acid metabolism.

[00:00:13]And let's discuss about the phenal ketonia. Final ketonia is the inborn error of metabolism. That means this error is present since birth and this is mostly genetic defect in the genes.

[00:00:25]That's why it is known as autotogomal recessive disorders and the mutation which takes place is the P gene mutation on the chromosome number 12 and this P gene is encoded for the phenile alanine hydroxil and this gene mutation lead to the classical PKU. Okay. Okay. So main enzyme defect in the PKU is the phenile alanine hydroxilates.

[00:00:47]As we already know in our previous lecture that phenile alanine is converted into tyrosins with the help of phenile hydroxil phenile alanine hydroxil and with the coenms of tetrabroerine and oxygen molecule along with NADH. So if there is defect in the penilein hydroxilates or tetraboterines or or the bioterine synthesis that may lead to the VKU. Okay. So let's discuss about the types of PKU. PKU1 or the PKU type one is the classical one that is due to the deficiency of the phenile alanine hydroxilase and PKU2 and three are due to the deficiency of dihydrobacterine reductage. Okay. This is required for the conversion of BH2 to BH4. That means it required for the further conversion of phenile to tyrosins. Okay. If there is defect in this then also lead to the PKU of type 2 and type three. Similarly in PK of type four and five deficency of bioterin synthesis enzyme is defect. Okay. So here the bioterin synthesis is defect that leads to the type four and five type of PKU. Okay. So this is all about the types of the PKU. Type 1 to five.

[00:01:52]Let's discuss about the biochemical abnormalities present in the PKU. As you know that the phenile alanine is cannot convert into tyrosin there is defect in the phenile phenile hydroxil enzyme.

[00:02:02]That's why it it undergo a minor pathway that is why phenile alanine is converted into phenile pyrovate with the help of trans amination reaction that is alpha ketoglutarate converted into glutamates and phenile converted to phenile pyroate. Similarly this phenile pyroate under go decaroxilation reaction while the removal of CO2 gives rise to phenile acetate. This phenile acetate is actually responsible for the mousy order of the skin mousy order of the urine and sweats. That's why with the PKU patients have a urine of mouse orders. Okay, this is a bio biochemical abnormality in the PKU. Similarly, let's see the clinical manifestation seen in the PKU. Okay, the first clinical manifestation is a mental retardation and the CNS manifestation.

[00:02:46]Okay, so the reason behind of mentalation, CNS manifestation is decreased synthesis of neurotransmitter like dopamine, norepinephine and epinephrine. As you know that spinal alan is converted in tyrosine and tyrosin is the from tyrosin dopamine norepinephrine epinephrine are produced.

[00:03:02]So if there is decrease in the tyrosin level that will ultimately lead to the dopamine norepinephrine epinephrine level of the neurotransmitter. Okay.

[00:03:09]Similarly in increased phenile alanine interferes with the tryptophan metabolism of the tryptophan uptake to the brains that lead to the decreased serotonin production. These two are the reason behind mental radation and CNS manifestation in the PKU or the classical PKU cases. Okay. So let's see the another clinical manifestation of the PKU that is hypopigmentation. There is a hypopigmentation is the features for the phenile kidonia. This is due to decreased level of tyrosine as we already know and also increased phenile aline interfere with the decrease action of the tyrosine enzymes. Tyrosin enzyme which is essential for the melanin production. Okay, that's why in the PKU patient there will be the blues eyes and hyperpigmentation of the skin and the also hair color is also changed. Okay, these are the clinical manifestation for hyperpigmentation and again we have a multi order of urine due to phenile acetates. This is all about the clinical manifestation and if we see about the laboratory diagnosis that is rapid screening test that is G3 test and gold standard test is tendon mass spectroscopic. is mostly this gold standard test is expensive one and the rapid screening test is the less expensive that's why go test is mostly prefer after the birth okay thank you everyone