Structural and Functional Analysis of Pullulanase Type 1 (PulA) from Geobacillus thermopakistaniensis

Pullulanase type I (PulA) is a debranching enzyme that specifically cleaves α-1,6-glycosidic linkages in pullulan. Pullulan has not only diverse applications in food industry but also has immune-stimulatory effects on B and T cells, and found to enhance the production of various anti-inflammatory cytokines in human. Moreover, pullulan has been suggested as a possible anti-cancer drug delivery agent without adjuvant due to its unique structure. The process of pullulan degradation is unresolved due to imprecise pullulanase structural characteristics. Therefore, the present study aimed to understand the structural and functional characteristics of pullulanase enzyme from Geobacillus thermopakistaniensis MAS1 strain using various computational approaches. The physio-chemical topographies and secondary structure of GT_PulA were explored using ProPram, InterPro and SMART. Various tools like I-TASSER, ModRefiner, RAMPAGE, PROCHECK and MOE 2009.10 were used to construct and verify the 3D structural model. The structural elucidation confirmed the significant domains, i.e., CBM48, CBM2, and TIM barrel having catalytically active residues, and conserved region YNGWDP. CBM2 domain along with TIM barrel has a capacity to bind different ligands and proved favorable for multiple substrate catalyses. These structural properties can have a potential effect on enhancing enzymatic activity of GT_PulA enzyme.