Figure 3: Spectral changes during metabolism catechol to cis,cis-muconic acid by biphenyl grown cell (a) catechol to 2-hydroxy-muconaldehyde by naphthalene grown cell (b) and salicylaldehyde to salicylic acid by naphthalene grown cell (c). The sample and reference cuvettes contained 50 mM potassium phosphate buffer (pH 7.0) in 1 ml volume. The sample cuvette also contained 30 nmol of catechol (panel a and b) and 75 nmol of salicylaldehyde (panel c). NAD+ (10 nmol) were also added to both cuvettes, in case of enzymatic transformation of salicylaldehyde (panel c). Spectra were recorded at an interval of 2 minutes, after the addition 50 μl of extract containing ~100 μg of crude protein. Up and down arrows indicate increasing and decreasing absorbance, respectively.