Mutations bringing about alterations in metabolic pathways, nutritional requirements etc. are called biochemical mutations.
These are mostly noticed in microorganisms. Biochemical mutations in Escherichia coli can be induced by repeated sub culturing.
In E. coli, the normal strains are called Paratrophs while the mutants are called Auxotrophs. These mutations are for some of the nutritional requirements like Biotene, Methionine, Leucine etc.
Image Source: glycob.oxfordjournals.org
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The paratroph is called genetically B+, M+ and L because it has the capacity to synthesize all these.
On mutation the auxotroph loses the capacity to synthesize these and consequently it is known as BML several metabolic disorders due to biochemical mutations have been in man also.
They are commonly called inborn errors in metabolism’. R6l30first such biochemical disorder to be reported was Alkaptoneuria (Garrod reates to a metabolic disorder concerning the amino acid phenyl Alkaptaneuric individuals have a mutated gene which does not produce enzyme homogentisate oxidase, resulting in the accumulation of entisic acid.
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In the cell, which is excreted along with the urine? Homogenticic acid is a strong reducing agent and gets oxidized in the presence of air into a black pigment, resulting in the black coloration of the urine.
Another biochemical mutation in man is phenyle ketoneuria. It is caused h a recessive mutant gene in which due to failure of conversion of phenylalanine to tyrosine, the former accumulates in the blood and excreted through the unne.
This leads to mental retardation. In addition to the above, Tyrosinosis, Albinism and Cretinism are the other metabolic disorders due to biochemical mutations.