APPB1; pectinesterase inhibitor. similar to invertase/pectin methylesterase inhibitor family protein [Arabidopsis thaliana] (TAIR:AT5G50030.1); similar to pollen-specific protein Bnm1 [Brassica napus] (GB:AAB48480.1); contains InterPro domain Pectinesterase inhibitor; (InterPro:IPR006501)