Study on Outer Chains Released from Amylopectin between Immobilized and Free Debranching Enzymes.

Abstract

, p. t-tO (ZOOI)J As amylopcctins iue vcry large molecules con-$tructcd from many shon-arnylose-chains, it i.c nor easy to eJucidate their frne stnlcturcs. Some model .s have been proposed by using the fundnmental A, B, and C chains, and a cluster structure proposed by Hizr:kuriD he.,i been accepred as rhe most reliable model. B and A chains are gencrul name$ lndicating shon-amylose-chains with and wirhour brnnching residue, rcspecdvcly. C chains flre onc of the B chains having a reducing+nd rcsidue and exi.sting only as a single chain in an amylopectin molecule. It is rcasonable to think that A cbains nre shortish chains and exist in the outer ponions of the clusrer lr[ructurc. Thc characreristics of A chains mighr be an importanr factor to rccognize the propertias of srarches becarrsc the posidon of A chains makes ir casier to tbrm double-helicul structures with neightrouring chains ancl interact with many other molccules likc tho.sc of waer nnd lipitls. Recently, we reported a method whilc .rtudying (172, Ohmatsubaru, Takaya-cho, Konan 4BJ-8086, Iupan) Various kinds of parrial hydrolysates of waxy nraize arnylopectin were preparcd by controlling the debrauching acdons of imruobilized and fiee isoamylusc, and frcc pullulanase, ard rhen frac-donatcd into ttrce fracdon.c by a gel chromatognrphy using Toyopearl I'IW-65F, Thc smrrllcs([rac-dons (fr. 3) were ossin ddbrmchcd with free isoamylase nnd nnalyzcd by HPAEC-PAD in order to obnrin informadon of chain disributions cxisting in rhe ourer porrion of amylopecdn molcculcs. About I0-159o of the panial hydrolyses were appropriate to collcct thc shonish chains released ftom amylopcctin. The chain disrriburion of thc smalle,cr fracdon consisted of rnauy shorr-chrrins wirh DP 6-15, atd ir could bc thought that nrost of the shortish chtrins might be A chains derived from outtr portions of amylopectin. 'fhe compunrtivc experiments lunong rhe debrsnching enzymes led us to confirnr thar poniel hydrolyzed materials obrsined by thc low cnzyme activiry of free isoaurylusc ord pullulunirsc could be used to study thc ourer chains of arnylopecrinS like inrmobi-lized isonnrylase. the partial hydrolysis of amylopectin with immobilized isonmylase, nnd it was found that chains ex. isting in thc outer portion of amylopecdn molecules were debranched preferentially ar the esrly stage of the hydrolysi.s." Supponr of about 100-mesh were used for immobilizadon of the enzymc, and it was consiclered that thc immobilized isoamyla-se i.r a debranching enzyme of va,rr hulk. The size of the amylopectin rnolecule nr the largest estimlte might be smsller than that of the immobilized isoamylase. So, it could be thought thert the inreracrion between subsunte and enzymc starts tiom the outside of the rrmylopectin molecule and shon-amylose-chains existittg in the outer portion of' thc amylopectin rnolecule were rclcascd rapidly. This analysis msthod was applied to a comporotive sudy of rwo rice surches (Koshihikfii uncl Reiho)-i) On the other hand, Manner.c and Marherson') reponed thar A chains were predominnntly ond sclectivcly rcmovcd with the portial hydmlysi.r of waxy maize amy-lopecrin by.pullulanase. There are only a few fe-pons srudying the pnrtial srucLurcli of amylopectin.