Fungisporin is a peptide hormone isolated from fungi. Its apparent molecular wei
ID: 72161 • Letter: F
Question
Fungisporin is a peptide hormone isolated from fungi. Its apparent molecular weight (determined by mass spectrometry) is 428. Treatment with ninhydrin, fluorescein, aminopeptidase, trypsin, or carboxypeptidase A caused no reaction. Treatment with chymotrypsin resulted in the formation of only one peptide. Two cycles of Edman degradation on this peptide gave Val and Val, respectively. Acid hydrolysis of fungisporin gave equimolar amounts of Val and Phe. Most surprisingly, however, the solution of acid-hydrolyzed fungisporin did not rotate plane-polarized light. Based on these data, propose a plausible structure for fungisporin.Explanation / Answer
Treatment with chymotrypsin yielding only one peptide gives an indication that the molecule has a cyclic structure. Only when a cyclic compound is cleaved, you will be getting one peptide.
Chymotrypsin cleaves at C-terminus of hydrophobic amino acids mainly tyrosine, tryptophan, and phenylalanine. So one of residue could be any of three.
Two cycles of Edman degradation giving Val and Val gives a hint that 2 molecules of Val are present.
Acid hydrolysis gave equimolar Val and Phe suggests that 2 molecules of both Val and Phe are present.
Plane polarized light was rotated by this solution confirms that this molecule is a cyclic molecule which does not have a chiral carbon.
The structure could be Val-Val-Phe-Phe in a cyclic form
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.