How does innovation arise in biological systems? A typical example is the emergence of novel catalytic functions in enzymes.
Hereafter I report two studies that come to contradicting conclusions.
Axe and Gauger suggest that the number of simultaneous mutations required to convert a 2-amino-3-ketobutyrate CoA ligase (Kbl2) to 8-amino-7-oxononanoate synthase (BioF2) are so many changes that it becomes probable only “on timescales much longer than the age of life on earth”.
Conversely, Jez and Penning showed that a single mutation changes D4-3-ketosteroid-5b-reductase to 3a-HSD; where Sommerville and coworkers have proved that six substitutions are sufficient to convert a hydroxylase to a desaturase.
How do we account for such contradicting results?
Does evolvability inversely correlate with specificity and catalytic proficiency?
Shall an enzyme be suboptimal adapted to its function in order to evolve new functions?
Does this apply to whole organism?
By Davide De Lucrezia
Gauger AK and Axe DD. The Evolutionary Accessibility of New Enzymes Functions: A Case Study from the Biotin Pathway. BIO-Complexity, Vol 2011
Jez JM and Penning TM. Engineering steroid 5b-reductase activity into rat liver 3a-hydroxysteroid ehydrogenase. Biochemistry 1998, 37:9695-9705.
Broun P, Shanklin J, Whittle E and Somerville C. Catalytic plasticity of fatty acid modification enzymes underlying chemical diversity of plant lipids. Science 1998, 282:1315-1317.