Biomedical subjects

F J Zahradník

Publications and source records attributed to F J Zahradník.

5 recordsLinked to original sources

PubMed2005

Quantitative analysis of streptococcal exoprotein flow to the host receptor--exact basis for therapy of tumors and Alzheimer's disease.

The basis of a bacterial pathogenic process consists in the change of a certain host structure to a completely different one. This is accomplished by binding of a bacterial protein product to the host structure. Streptococcal NAD+-nucleosidase was explored as to its binding to the host receptor represented by beef heart extract. The bacterial product was found to bind to the host structure until the available host structure was fully saturated. The similarity of the above flows of macromolecules with some models of morphogenesis indicates the existence of diseases associated with the flow of a protein to the undesirable site in the organism. In such a case therapy with low-molar-mass substances is wrong in principle.

Alzheimer Disease↗

PubMed2001

Kinetic properties of fractions of extracellular NAD+ nucleosidase from Streptococcus pyogenes as an example of host selection by a pathogen: possible role of serum albumin in the organism.

Preparative isoelectric focusing was used to separate free bacterial NAD+ nucleosidase from its complex with a bound host component. Both fractions were characterized by optimum temperature and activation energy of denaturation. The bacterial product is enzymically inactive. The enzymically active structure is formed upon binding to the host component. Only the host organism can provide the suitable, activating structure. The host component in the present system is added to the cultivation medium with a beef heart extract but it can be replaced by serum albumin. The possible role of albumin as a carrier structure for flexible and enzymically inactive peptides is discussed. Different peptides bound to albumin can provide different enzyme activities. The term binary enzyme is coined, referring to a situation where the two enzyme components are coded at genetically distant loci. The pathogen makes use of the carrier structure of albumin type and produces another polypeptide invested with an enzyme activity convenient for the pathogen.

Culture Media↗

PubMed2000

Enzymes are open systems.

The exchange of mass, energy, and information with the environment typical of open systems can also be found in enzymes. An enzyme is able to receive information on substrate concentration in an arbitrary concentration range. This actually follows from the elementary solution of Michaelis-Menten kinetics. The Michaelis constant can be seen as a relation between the decreasing parameter of a zero-order reaction and the increasing parameter of a first-order reaction over a certain time interval. This excludes the state of zero-order kinetics and consequently the state of zero content of concentration information.

Enzymes↗

PubMed1980

Streptococcal extracellular NAD+ nucleosidase. Characterization of changes occurring during purification.

Purification of streptococcal extracellular NAD+ nucleosidase is associated with changes of kinetic properties. A high-molecular weight component is required for a full activity of the enzyme. The component is not produced by bacteria and is present in the Todd-Hewitt cultivation medium, the beef-heart extract serving primarily as its source. In its effect on the enzyme this component can be replaced with bovine albumin. It follows from the time relationship of the NAD decomposition that the mechanism of the studied enzymic reaction is not hydrolytic. In addition to nicotinamide, a product of polymeric character is formed.

Animals↗

PubMed1977

Streptococcal extracellular NAD-glycohydrolase. Optimal temperature and activation by cysteine.

Streptococcal extracellular NAD-glycohydrolase (EC 3.2.2.5) exists in two distinct states with respect to the optimal reaction temperature. Bacteria produce the enzyme form with optimum activity at about 40 degress C. Probably due to oxygen action, the enzyme is converted to a form with optimum activity at 30 degrees C. Compounds of the type of cysteine restore the initial state. The conversions are accompanied by enzyme activity fluctuations.

Cysteine↗