Involved in the biosynthesis of paerucumarin, a cyclized isocyano derivative of tyrosine (PubMed:18689486, PubMed:18824174). Responsible for the synthesis of the isonitrile group on tyrosine using the C2 of ribulose 5-phosphate as the source of the carbon atom (Probable). D-ribulose 5-phosphate + L-tyrosine = (2S)-3-(4-hydroxyphenyl)-2-isocyanopropanoate + formaldehyde + H(+) + H2O + hydroxyacetone + phosphate Monomer in solution. Disruption of the gene maintains the ability of the strain to produce the pyoverdine siderophore (PubMed:18689486, PubMed:18824174). Disruption mutant cannot produce paerucumarin (PubMed:18689486). Belongs to the isocyanide synthase family.