H. Iefuji et al., RAW-STARCH-DIGESTING AND THERMOSTABLE ALPHA-AMYLASE FROM THE YEAST CRYPTOCOCCUS SP. S-2 - PURIFICATION, CHARACTERIZATION, CLONING AND SEQUENCING, Biochemical journal, 318, 1996, pp. 989-996
A starch-degrading enzyme produced by the yeast Cryptococcus sp. S-2 w
as purified in only one step by using an alpha-cyclodextrin-Sepharose
6B column, and was characterized as an alpha-amylase (EC 3.2.1.1). The
molecular mass and isoelectric point of purified a-amylase (AMY-CS2)
were estimated to be 66 kDa and 4.2 respectively. AMY-CS2 has raw-star
ch-digesting and raw-starch-absorbing activities. Furthermore it was s
hown to be thermostable. An open reading frame of the cDNA specified 6
11 amino acids, including a putative signal peptide of 20 amino acids.
The N-terminal region of AMY-CS2 (from the N-terminus to position 496
) had 49.7% similarity with the whole region of a-amylase from Aspergi
llus oryzae (Taka-amylase), whereas the C-terminal region had a sequen
ce that was similar to the C-terminal region of glucoamylase G1 from A
. niger. In addition, putative raw-starch-binding motifs exist in some
amylolytic enzymes. A mutant AMY-CS2 that lacks the C-terminal domain
lost not only its ability to bind or digest raw starch, but also its
thermostability. Consequently it is possible that the putative raw-sta
rch-binding domain of AMY-CS2 plays a role not only in the molecule's
raw-starch-digesting ability but also in its thermostability.