Chlorophyll, heme, vitamin B12, and a host of other substances are bio-synthesized from porphohilinogen (PBG), which is itself formed from condensation of two molecules of 5-aminolevulinate. The two 5-aminolevulinates arc bound to lysine (Lys) amino acids in the enzyme, one in the enamine form and one in the imine form, and their condensation is thought to occur by the following steps. Using curved arrows, show the mechanism of eachstep.

Transcribed Image Text:

Co," co, Co2- Co co, Lys На wZLys Lys Lys :NH2 NŽLYS 'N. H2N NH2 Н NH2 NH2 Н Enzyme-bound 5-aminolevulinate co, co,- co,- Co2 co,- NZLYS H2 н N. NH2 н NH2 NH2 Н Porphobilinogen (PBG)