Year: 1936
Type: article
Abstract: VAN KLINKENBERG [1934] suggested that oc-amylases promote hydrolysis of "ac-starch" (which is a fraction resembling Wijsman's "erythrogranulose" or Baker's "oa-amylodextrin" and constitutes about 36 % of the starch).fi-Amylases were correspondingly specific for fl-starch (the remainder).Hydro- lysis beyond 36 % in presence of ac-amylase was explained by the supposed slow transformation of fiinto oc-starch.Now starch in solution contains certain distinct components which may be fractionated by electrodialysis yielding re- spectively amyloamylose (blue with iodine) and erythroamylose (red with iodine) [Samec and Mayer, 1921].Amyloamylose is hydrolysed by pancreatic (ac-), barley (fi-) and unfractionated malt (mixture) amylases relatively easily and completely, but erythroamylose only with difficulty [Samec and Waldschmidt-Leitz, 1931, this paper Table I].Thus Van Klinkenberg's so-called ac-and fl-starches are not identical with amylo-and erythro-amyloses, though they might represent fractions of the erythroamylose, which constitutes at least 60 % (recovered by us) to 83 % (Samec) of the total starch.ac-Malt-amylase does not selectively hydrolyse the erythrogranulose or ac- amylodextrin fraction of starch [Hanes, 1935; this paper Table I].In this communication are reported observations on the kinetics of hydrolysis promoted by acand 3-amylases or by their mixtures.The substrates included starch, amyloamylose, erythroamylose (components of starch), a-amylodextrin and certain fission products of the enzyme actions.oc-Amylodextrin may be regarded either as a component of the original starch or as a fission product of the action of ,3-amylase. EXPERIMENTAL.Substrates.Lintner soluble starch as described in Part I. oc-Amylodextrin was prepared from the soluble starch by the action of alcohol-precipitated barley amylase at PH 4X6 and 500 by a method closely resembling that described by Baker [1902]; yield 33 %, [ac] `+1880, reducing power (R) 1 % as maltose.Glycogen (Pfan- stiehl), [ac] '+ 185°, R 0 7 %.Achroodextrin was prepared from soluble starch by the action of commercial (B.D.H.) pancreatin at PH 6X8 and 250 until the reducing power corresponded to 51 % as maltose, the dextrin being precipitated in and washed by 80 % boiling alcohol until the washings were free from reducing power and finally dried over H2504 at 600; yield 46 %' " + 160-60, R 32.8% ( 446
Source: Biochemical Journal
DOI: 10.1042/bj0300446
Institution: University of Birmingham
Language: English
Subfield: Biotechnology
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W68920490