InterPro domain: IPR006501

This domain inhibits pectin methylesterases (PMEs) and invertases through formation of a non-covalent 1:1 complex [ 1 ]. It has been implicated in the regulation of fruit development, carbohydrate metabolism and cell wall extension [ 2 ]. It may also be involved in inhibiting microbial pathogen PMEs. It has been observed that it is often expressed as a large inactive preprotein [ 3 ]. It is also found at the N-termini of PMEs, suggesting that both PMEs and their inhibitor are expressed as a single polyprotein and subsequently processed. It has two disulphide bridges and is mainly alpha-helical [ 3 ].

1. A glycoprotein inhibitor of pectin methylesterase in kiwi fruit. Purification by affinity chromatography and evidence of a ripening-related precursor. Eur. J. Biochem. 233, 926-9
2. Kiwi protein inhibitor of pectin methylesterase amino-acid sequence and structural importance of two disulfide bridges. Eur. J. Biochem. 267, 4561-5