Amino acid tropical fruits

An unknown acetylenic amino acid obtained from the seed of a tropical fruit has the molecular formula C7H11NO2. On catalytic hydrogenation over platinum this amino acid yielded homoleucine (an amino acid of known structure shown here) as the only product. What is the structure of the unknown amino acid ... 

Papain, EC 3.4.22.2, the archetype of cysteine peptidases. It was isolated from the latex of the tropical papaya fruit (Carica papaya). Papain is a single-chain protein (212 aa 23 kDa) containing three disulfide bonds and a known three-dimensional structure with 1.65 A resolution The catalytic amino acid residues have been identified as Cys, His and Asn, whereas Gln helps to stabilize the oxyanion hole. Papain has a fairly broad specificity [J. R. Kimmel, E. L. Smith, J. Biol. Chem. 1954, 207, 515 A. C. Storer, R. Menard, Methods Enzymol. 1994, 244, 486]. 

Monellin is extracted from the fruit Dioscoreophyllum volkensii (syn. D. cumminsii, Menispermaceae) native to tropical African rainforests. Monellin is a sweet protein with liquorice-like flavour, which consists of two peptide chains, A and B, composed of a sequence of 45 and 50 amino acids, respectively (11.5 kDa). Under food processing conditions it is unstable and has no practical significance as a sweet substance. 

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