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The Evidence of the Enzymes

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Archives / 1975 / September

 

 

The Evidence of the Enzymes

G.T. Javor
-an associate professor of chemistry at Andrews University, Berrien Springs, Michigan at the time this article was written

 

 

MOLECULES are small particles in visible to the naked eye. They are com posed of two or more fundamental bits of matter called atoms. All substances around us, and we ourselves, are a collection of atoms and molecules. In the past few decades a great deal of new in formation has become available about the nature of molecules found in living organisms. When we consider what has been learned, the personality of a very wise, meticulous and loving Designer emerges with ever-increasing clarity.

In this article we will consider briefly a special class of molecules called enzymes. Enzyme is a household word to day, thanks to the educational power of laundry commercials. Who doesn't know that presoaking one's laundry in an enzyme-containing agent will cause the removal of most stubborn stains? Actually, there are thousands of different enzyme molecules, all with different functions. The detergent industry is using only a few of these.

The word enzyme comes from the Greek language; it means "in yeast." The word was introduced about one hundred years ago to describe agents found in yeast that caused the conversion of glucose to alcohol. In the modern definition enzymes are promoters or catalyzers of specific chemical changes. They are made up mostly of proteins.

Naturally-occurring enzymes are found only in living tissues. However, if one extracts these catalysts from their natural environment, they are as capable of enhancing the rates of chemical conversions in a test tube as inside the living organism. It is not uncommon for an enzyme to speed up a chemical process by a factor of one hundred million. This means that if in the presence of the enzyme a chemical event occurs in one second, in its absence the same reaction would be completed in about four months!

Within the past few years it has become possible to artificially synthesize some enzymes. This brilliant techno logical feat was first achieved in 1969 by joining one hundred twenty-four amino acids in a predetermined sequence, using a highly automated instrument specifically designed for this purpose. The name of this enzyme is Ribonuclease, and its synthesis took about twenty-seven hours. 1 These synthetic molecules were exact duplicates of the naturally occurring enzyme, which incidentally is produced within a few seconds by our body tissues.

As catalysts, the enzymes them selves are not altered by the act of speeding up chemical reactions. They appear to bring the potentially reactive molecules (usually much smaller than the enzymes themselves) into close contact and proper orientation with one another, allowing them to interact under optimized conditions.

Figure 1 shows a portion of the metabolic conversions occurring inside a typical cell. Each arrow represents a chemical reaction, promoted by a specific enzyme. If that enzyme is not present in the cell the indicated chemical reaction will not take place.

Consequences of Missing Enzymes

There are at least forty-nine disorders known to man that are a direct consequence of missing or inactive enzymes in the tissues.2 Because the presence or absence of these enzymes is determined by the genetic makeup of the person, these diseases may be passed on to one's children.

These illnesses are brought on, as mentioned, by the inadequacy of a single enzyme among the tens of thousands of other enzymes that are fulfilling their functions normally. This dramatically underscores the essential nature of each of these biological catalysts.

For the sake of accuracy, it should be mentioned that not all chemical reactions are continuous in the cells. Thus there are enzymes that are called upon as catalysts only under special conditions. Obviously a nonfunctioning enzyme in this category would be missed only if the need for it arose.3

If an enzyme is not catalyzing properly, the metabolic intermediate customarily handled by it accumulates. This is illustrated in Figure 2. Here substance A is converted to substance B in five separate steps, each step requiring the presence of a different enzyme. If enzyme 3 is defective, for example, substance A will be converted to intermediate II, and this compound accumulates. Frequently these intermediates have no function in the cell except to be a transitory substance between two useful compounds. Sometimes large concentrations of these intermediates are even harmful, and have growth-inhibitory effects on the cell.

There is much in this state of affairs that argues against the chance occurrence of living matter. While there are overwhelming odds against the spontaneous formation of a single functional enzyme from a random collection of amino acids,4 it is even more impossible for a complete set of enzymes to come upon the scene simultaneously, in close vicinity of each other, so that all of these can be gathered up suddenly into a single cell. And the simplest of cells known today need thousands of enzymes to promote chemical reactions associated with life. Dixon and Webb in their well-known monograph discuss the origin of enzymes. We quote:

"Let us now suppose that in some way proteins did come into existence: even if they had enzymatic properties there is no reason why their activities should be related, and it is highly improbable that they would form a continuous chain such as we have seen is necessary for the trapping of energy and its utilization for the biosynthetic reactions which constitute life. Yet the occurrence of a single gap would prevent the development of the system. ... A further difficulty is that of holding the components of the system together until a cell membrane is formed, assuming life to have begun in the ocean. Unless the ocean contained throughout a fairly high concentration of the components (thus being itself one gigantic living cell!), the components would rapidly disperse as hap pens now when a cell membrane is ruptured. . . . Thus the whole subject of the origin of enzymes, like that of the origin of life, which is essentially the same thing, bristles with difficulties." 5

The evolutionary scheme requires organisms to change into radically new and more complex forms with the passage of time. This process involves the development of new metabolic path ways and the synthesis of new substances. In the frequent cases that require several independent chemical reactions in the cell to convert one substance into another, an evolving organism capable of performing only one or two of the intermediate steps, producing intermediate substances that are useless or even destructive to the organism, would hardly survive the postulated evolutionary selective pressures. Therefore a step by step scheme of evolving new metabolic pathways will not work even if one accepts the premises of evolution. Nothing less than the sudden appearance of all the enzymes necessary for that particular metabolic sequence would do. And this is too great a gap to surmount by existing evolutionary theories.

Even to a casual observer the meticulous design of metabolic pathways can be apparent. But further probing into this topic rewards the searcher with additional evidences of the genius of our Maker. For instance, frequently enzymes with identical functions are found in different parts of the human body. However, the structures of these identical-function enzymes sometimes differ slightly. Enzymes that have identical functions but differing structures are called iso-enzymes or isozymes.

One enzyme that is found in several forms in human tissue is lactic acid dehydrogenase. This enzyme promotes the rapid conversion of pyruvic acid to lactic acid. Glucose, the most important carbohydrate source of energy, is broken down to carbon dioxide and water in two stages, as shown in Figure 3. The first stage of breakdown does not require the presence of oxygen and ends with pyruvic acid. If there is no oxygen present pyruvic acid is converted to lactic acid, which is then taken to the liver where it is used to make more glucose. In the presence of oxygen, however, pyruvic acid can be further metabolized with the release of substantial additional amounts of energy.

The form of lactic acid dehydrogenase found in skeletal muscle has a high affinity for pyruvic acid, promoting its very rapid conversion to lactic acid. And frequently the oxygen supply in the muscles is not adequate to permit the total breakdown of glucose. On the other hand, in heart or kidney tissue we find an isozyme of lactic acid dehydrogenase with low affinity for pyruvic acid. Under normal circumstances there is a plentiful supply of oxygen in these tissues, and pyruvic acid produced from glucose can be readily degraded further to carbon dioxide and water. Here the only role of lactic acid dehydrogenase is that of an emergency mechanism to remove pyruvic acid that would accumulate under unusual conditions.

Obvious Design and Planning

Another example of obvious design and extensive planning is found upon consideration of enzyme cofactors. While all enzymes are made mostly of proteins, a number of these promoters of chemical reactions are totally incapable of functioning unless a small nonprotein molecule is attached to them. These nonprotein parts are called cofactors.

Our body cells can invariably manufacture the large protein molecules (unless there is a genetic disorder, referred to above), but often they are unable to produce the small nonprotein cofactor portion. These must be supplied with the food one eats. Many of the vitamins, especially the water soluble ones, are nothing more than cofactors needed for the functioning of certain enzymes.

We read in the Bible that the Creator specified what sort of food man should eat. "And God said, Behold, I have given you every herb bearing seed, which is upon the face of all the earth, and every tree, in which is the fruit of a tree yielding seed; to you it shall be for meat" (Gen. 1:29). Is it just a coincidence that the cofactors our enzymes need happen to be found in ample amounts in the food sources specified by the Creator?6 The answer has to be an emphatic No!

Nature can be studied on many different levels. On the molecular level this brief consideration of enzymes prompts one to join the psalmist in say ing: "O Lord, how great are thy works! and thy thoughts are very deep" (Ps. 92:5).

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FOOTNOTES

1. B. Gutte and R. B. Merrifield, "The Total Synthesis of an Enzyme With Ribonuclease A Activity," J. Am. Chem. Soc. 91: 501, 1969.

2. H. Sober (ed.), Handbook of Biochemistry (The Chemical Rubber Co., 1968).

3. E. Magnusson, "Control Systems and Evolution," The Ministry, December, 1974.

4. G. T. Javor and G. E. Snow, "The Apollo Sixteen Mission and Biochemical Evolution," Review and Herald, March 14, 1974.

5. M. Dixon and E. C. Webb, Enzymes (Academic Press Inc., Second Edition, 1964), p. 668.

6. Cyanocobalamine, or vitamin 812, is an exception, in that in plants it occurs only in low quantities.

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