Crystallization and preliminary X‐ray analysis of a protease inhibitor from the latex of Carica papaya

A Kunitz‐type protease inhibitor purified from the latex of green papaya ( Carica papaya ) fruits was crystallized in the presence and absence of divalent metal ions. Crystal form I, which is devoid of divalent cations, diffracts to a resolution of 2.6 Å and belongs to space group P 3 1 or P 3 2 . This crystal form is a merohedral twin with two molecules in the asymmetric unit and unit‐cell parameters a = b = 74.70, c = 78.97 Å. Crystal form II, which was grown in the presence of Co 2+ , diffracts to a resolution of 1.7 Å and belongs to space group P 2 1 2 1 2 1 , with unit‐cell parameters a = 44.26, b = 81.99, c = 140.89 Å.