Determine which of these statements describing the cytochrome P450 family of enzymes or the
mechanism of action are true.
a) The iron in cytochrome P450s can exist in both Fe2 and Fe3 states in a single catalytic cycle.
b) The coenzyme NADPH can serve as a source of electrons for cytochrome P450s.
c) Fe3 acts as a general base during the catalytic cycle.
d) Each cytochrome P450 isoform can act on only one specific organic substrate.
e) Cytochrome P450 uses molecular oxygen (O2) as a reactant.
f) The activity of cytochrome P450 generally results in carboxylated products.
Please include an explanation with your answer! Thank you.
Solution
Cytochrome P450 is a class of enzymes essential for many metabolic reactions. This includes
about 50 enzymes. ‘Heme’ is the cofactor of all these enzymes, means ‘heme’ is present in the
active site of the enzyme. ‘Heme’ shifts from Ferrous and ferric states as electrons are accepted
and donated. So, statement (a) is totally correct. And this iron component is present in the centre
of porphyrin ring. So, single/same catalytic site is there for ferrous and ferric.
In mitochondria, electrons are transferred from NADPH by cytochrome P450 reductase. So,
statement (b) is correct.
Base is anything which accepts protons. Fe3 (ferric) accepts protons from oxygen in
mitochondria. So, statement (c) is also correct.
Statement (d) is incorrect. There are several isoforms of P450. Among these CYP3A4 is the most
important. It metabolizes nearly half of the total drugs used in clinical biology nowadays. These
include codeine, acetaminophen, erythromycin etc. So, one isoform would act on many organic
substrates.
Statement (e) is correct. Yes, it uses molecular oxygen, and converts it to water.
Statement (f) is incorrect. Activity of cytochrome P450 resulted in formation of water (by
reduction of oxygen); this is not a carboxylated product..
Determine which of these statements describing the cytochrome P450 f.pdf
1. Determine which of these statements describing the cytochrome P450 family of enzymes or the
mechanism of action are true.
a) The iron in cytochrome P450s can exist in both Fe2 and Fe3 states in a single catalytic cycle.
b) The coenzyme NADPH can serve as a source of electrons for cytochrome P450s.
c) Fe3 acts as a general base during the catalytic cycle.
d) Each cytochrome P450 isoform can act on only one specific organic substrate.
e) Cytochrome P450 uses molecular oxygen (O2) as a reactant.
f) The activity of cytochrome P450 generally results in carboxylated products.
Please include an explanation with your answer! Thank you.
Solution
Cytochrome P450 is a class of enzymes essential for many metabolic reactions. This includes
about 50 enzymes. ‘Heme’ is the cofactor of all these enzymes, means ‘heme’ is present in the
active site of the enzyme. ‘Heme’ shifts from Ferrous and ferric states as electrons are accepted
and donated. So, statement (a) is totally correct. And this iron component is present in the centre
of porphyrin ring. So, single/same catalytic site is there for ferrous and ferric.
In mitochondria, electrons are transferred from NADPH by cytochrome P450 reductase. So,
statement (b) is correct.
Base is anything which accepts protons. Fe3 (ferric) accepts protons from oxygen in
mitochondria. So, statement (c) is also correct.
Statement (d) is incorrect. There are several isoforms of P450. Among these CYP3A4 is the most
important. It metabolizes nearly half of the total drugs used in clinical biology nowadays. These
include codeine, acetaminophen, erythromycin etc. So, one isoform would act on many organic
substrates.
Statement (e) is correct. Yes, it uses molecular oxygen, and converts it to water.
Statement (f) is incorrect. Activity of cytochrome P450 resulted in formation of water (by
reduction of oxygen); this is not a carboxylated product.
