Maltose inhibition

It was reported that maltose inhibits the hydrolysis of starch by malt a-amylase. The following data were obtained ... 

Product Inhibition. In most microbiological and biochemical systems accumulation of end products exercises an inhibitory effect on the rate of the forward reaction. Stimulation by end product is thermodynamically improbable. One of the major products of hydrolysis of cellulose is cellobiose. There is a stimulation by cellobiose of Cx activity of Streptomyces spp. filtrates only when the substrate is solubilized by the introduction of various substituents—e.g., CMC, hydroxycellulose, cellulose acetate, etc. Stimulation is absent when unsubstituted cellulose is used (14). On the other hand, product inhibition is common. Cellobiose inhibits the hydrolysis of cellulose by filtrates of most of the 36 organisms tested. This action of cellobiose is believed to be that of an end product inhibiting an enzymatic hydrolysis in much the same manner that maltose inhibits hydrolysis of starch by a-amylase. The inhibitory effect of products varies with the organism from which the cellulase is derived. Thus, lactose is a very good inhibitor of the enzyme from... 

The converted mash is pumped to a clean sterilised fermentor and the yeast inoculum is added. The set temperature range for whiskey fermentation of 72 hours is usually 17—21°C. At the beginning, the mash converted composition is approximately 80% sugars, mainly maltose and some (<1%) dextrose (primary conversion). The pH is adjusted to reduce initial bacterial growth. Grain neutral spidts are usually set at 27—29°C to expedite fermentation. Temperatures above 35°C inhibit yeast reproduction and promote rapid bacterial growth. Above 40°C actual yeast kill occurs. 

The third group is that of compounds which may potentially be transported by the PTS and inhibit cAMP production. Cellulase synthesis is initiated after these compounds are consumed for cell growth. This group includes D-glucose, D-fructose, maltose, mannitol, glycerol, sorbitol, and -methyl glucoside. The presence of these compounds in Solka Floe fermentations, enhanced enzyme yields (132 to 254%) but the time required to complete cellulase synthesis took longer (106 to 148%) than the control. 

Palacios, J. and Serrano, R. (1978). Proton permeability induced by polyene antibiotics. Aplausible mechanism for their inhibition of maltose fermentation in yealsEBS Lett, 91,198-201. 

Maltase Maltose 2.5-20 Mixed-type inhibition KmaDD = 2Kp, at 10 mg/ml... 

Most of the acceptors, such as maltose, isomaltose, and methyl a-D-glucopy-ranoside, were apparent competitive inhibitors for dextransucrase, as determined by Lineweaver-Burke or Hanes-Woolf plots103 however, when higher sucrose concentrations were used in a Michaelis-Menten plot, the inhibition was not reversed for methyl a-D-glucopyranoside as it should have been for a competitive inhibitor.103 It was concluded that the acceptors were being bound at a site that was separate and distinct from the sucrose binding-sites. 

The curves shown indicate that ONPTG, maltose, and melibiose, in the range of the concentrations used, inhibit the O-nitrophenyl galactoside hydrolysis rate. We can see from the curves that a plateau is not reached at the high concentrations of inhibitors, meaning that the maximum velocity Vm is not reached. Thus, in order to determine Vm and Km, reciprocal plots should be drawn (Figure 17.6). 

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