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Advances in enzymology and related subjects of biochemistry. Vol. 23
BOOK REVIEWS
556
in transfer reactions and molecular rearrangements, as well as the mechanisms of coenzyme binding. Two aspects of sulfur biochemistry are discussed in the articles ‘Synthesis and Hydrolysis of Sulfate Esters” (Roy) and “The Biochemistry of Sulfonium Compounds” (Shapiro and Schlenk). The metabolism of sulfate esters has only recently attracted the attention of biochemists. The steps in the enzymatic synthesis of “active” sulfate and the properties of sulfokinases and sulfatases are comprehensively discussed. Shapiro and Schlenk review the biosynthesis of “active” methionine and the related sulfonium compounds, and their many biochemical functions. Both articles point out the areas of uncertainty and the many deficiencies in knowledge about these compounds and their related enzyme systems, and indicate the avenues of approach necessary for their clarification and elucidation. The elegant scheme of cholesterol biosynthesis is recounted by Popjak and Cornforth; emphasis is placed upon the recently discovered intermediary stages of mevalonic acid and squalene formation, and the enzyme systems involved in their biosynthesis, which as yet are incompletely characterized. While the overall scheme of cholesterol synthesis has been defined, it is evident that major obscurities still exist in several places, and that much work is still required to elucidate the details of the many steps of t,he scheme. The authors also indicate the probable existence of common biosynthetic pathways between the sterols and the polyisoprenoid compounds, which promise to be an area of interesting research. The application of column chromatography as a technique for the separation and purification of enzymes is discussed by Turba. A qualitative theory for this phenomenon is formulated. However, since our knowledge of the properties of resins are yet incomplete, and since physicochemically undefined proteins are used, the theory seems to have little pertinence at this time. Many chromatograms of enzymes are shown; it is apparent that the separation of individual enzymes from other proteins by column chromatography remains empirical. All the articles in this volume cover their topics thoroughly, and as such are always valuable as sources of literature reference. In spite of the wide variation in the state of development of the areas covered, most authors were able not only to contribute intellectually towards the understanding of the subject, but also to offer insight into certain problems of current interest. These thoughts will provoke and direct further experimentation and make the subjects interesting even to the casual reader. BERT L. VALLEE,
Boston,
Massachusetts
Advances in Enzymology and Related Subjects of Biochemistry. Vol. 23. Edited by F. F. NORD. Interscience Publishers, New York, N. Y., 1961. vi + 557 pp. Price $12.50. The current volume of Advances in Enzymology is an interesting mixture of reviews that will be of great value to workers in certain areas of enzymology and of articles that will entertain those concerned with related subjects of biochemistry. The papers by Racker on “Mechanisms of Synthesis of Adenosine Triphosphate” and by Kornberg and Elsden on “The Metabolism of a-Carbon Compounds by Microorganisms” are timely and stimulating reviews of several aspects of intermediary metabolism from the points of view of energy production and the synthesis of cell material. Racker has surveyed the problems of oxidative phosphorylation against a background of the more completely understood substrate-level reactions that lead to adenosine triphosphate (ATP) formation, and has presented the findings and problems resulting from many independent approaches to the study of a process that has yet to be identified. Kornberg and Elsden have described several sequences of reactions that permit 2-carbon compounds to be converted to larger molecules, especially to pyruvate. The recently discovered condensation of glyoxylate and acetyl-coenzyme A to form malate and the production of tartronic semialdehyde and COP from glyoxylate have permitted schemes to be established for the utilization of acetate, glycolate, glyoxylate, oxalate, and glycine for energy and cell synthesis. The review shows nicely the properties of several biological systems and also describes several unresolved metabolic problems. Three articles are more classical reviews of specific materials. Mandl has surveyed very comprehensively the literature on collagenases and elastases, two distinct groups of enzymes that attack connective tissue proteins. Desnuelle has documented the properties of pancreatic lipase, an enzyme that he carefully distinguishes from e&erases, especially by its requirement for an emulsified substrate. The iron prophyrin proteins whose similar spectral characteristics fall within those defined for Group A are described in an article by Lemberg. While the structure of the heme and many of the biological properties of these compounds have not been established (for example, the existence of a cytochrome a3 is st,ill the subject of controversy), the evidence and arguments are fully and fairly presented to give an appreciat,ion of the present status of these obriously important pigments. A brief paper by Wagner and Folkers summarizes the history of mevalonic acid during the five years since its discovery. Since the biochemistry of trrpene synthesis was described in detail
BOOK in the previous volume, it is reasonable that the present article is restricted to the chemistry of mevalonic acid. Some aspects of protein chemistry are reviewed in two articles by workers in Japan. Mizushima and Shimanouchi have presented some of the factors involved in the determination of the configurat,ion of polypeptide chains. Snalogies with simple models have led to the description of several configurations whose stabilities can be compared. The article concludes, however, with a recognition of the controlling role of the specific amino acid chains, &lose effects have not yet been analyzed. Okunuki has summarized in detail his analyses of protein configuration, based primarily on sensitivity of various preparations of protein to hydrolysis by an enzyme crystallized from Bacillus subtilis. A novel mathematical analysis of enzyme re-
557
REVIEWS
actions by Christiansen purports to show how rcactions in solution can proceed in discontinuous steps. The model proposed, in which the enzyme molecules in a given solution act synchronously and in which reverse reaction steps are considered to have no activation energy, will probably be found by most investigators to have little applicability to the enzyme systems they are studying. These considerat,ions seem more relevant than the mathematics of the article and convince this reviewer that periodicity in biological reactions must be explained with the use of factors that do not occur in simple enzymic reactions. The broad range of authoritative reviews includcd in this volume will commend it to all who harr found previous volumes of this series to be an effective means for retaining an orientation in the rapidly expanding field of enzymology.
ALMS H. MEHLER, Bethesda,
Maryland
556
in transfer reactions and molecular rearrangements, as well as the mechanisms of coenzyme binding. Two aspects of sulfur biochemistry are discussed in the articles ‘Synthesis and Hydrolysis of Sulfate Esters” (Roy) and “The Biochemistry of Sulfonium Compounds” (Shapiro and Schlenk). The metabolism of sulfate esters has only recently attracted the attention of biochemists. The steps in the enzymatic synthesis of “active” sulfate and the properties of sulfokinases and sulfatases are comprehensively discussed. Shapiro and Schlenk review the biosynthesis of “active” methionine and the related sulfonium compounds, and their many biochemical functions. Both articles point out the areas of uncertainty and the many deficiencies in knowledge about these compounds and their related enzyme systems, and indicate the avenues of approach necessary for their clarification and elucidation. The elegant scheme of cholesterol biosynthesis is recounted by Popjak and Cornforth; emphasis is placed upon the recently discovered intermediary stages of mevalonic acid and squalene formation, and the enzyme systems involved in their biosynthesis, which as yet are incompletely characterized. While the overall scheme of cholesterol synthesis has been defined, it is evident that major obscurities still exist in several places, and that much work is still required to elucidate the details of the many steps of t,he scheme. The authors also indicate the probable existence of common biosynthetic pathways between the sterols and the polyisoprenoid compounds, which promise to be an area of interesting research. The application of column chromatography as a technique for the separation and purification of enzymes is discussed by Turba. A qualitative theory for this phenomenon is formulated. However, since our knowledge of the properties of resins are yet incomplete, and since physicochemically undefined proteins are used, the theory seems to have little pertinence at this time. Many chromatograms of enzymes are shown; it is apparent that the separation of individual enzymes from other proteins by column chromatography remains empirical. All the articles in this volume cover their topics thoroughly, and as such are always valuable as sources of literature reference. In spite of the wide variation in the state of development of the areas covered, most authors were able not only to contribute intellectually towards the understanding of the subject, but also to offer insight into certain problems of current interest. These thoughts will provoke and direct further experimentation and make the subjects interesting even to the casual reader. BERT L. VALLEE,
Boston,
Massachusetts
Advances in Enzymology and Related Subjects of Biochemistry. Vol. 23. Edited by F. F. NORD. Interscience Publishers, New York, N. Y., 1961. vi + 557 pp. Price $12.50. The current volume of Advances in Enzymology is an interesting mixture of reviews that will be of great value to workers in certain areas of enzymology and of articles that will entertain those concerned with related subjects of biochemistry. The papers by Racker on “Mechanisms of Synthesis of Adenosine Triphosphate” and by Kornberg and Elsden on “The Metabolism of a-Carbon Compounds by Microorganisms” are timely and stimulating reviews of several aspects of intermediary metabolism from the points of view of energy production and the synthesis of cell material. Racker has surveyed the problems of oxidative phosphorylation against a background of the more completely understood substrate-level reactions that lead to adenosine triphosphate (ATP) formation, and has presented the findings and problems resulting from many independent approaches to the study of a process that has yet to be identified. Kornberg and Elsden have described several sequences of reactions that permit 2-carbon compounds to be converted to larger molecules, especially to pyruvate. The recently discovered condensation of glyoxylate and acetyl-coenzyme A to form malate and the production of tartronic semialdehyde and COP from glyoxylate have permitted schemes to be established for the utilization of acetate, glycolate, glyoxylate, oxalate, and glycine for energy and cell synthesis. The review shows nicely the properties of several biological systems and also describes several unresolved metabolic problems. Three articles are more classical reviews of specific materials. Mandl has surveyed very comprehensively the literature on collagenases and elastases, two distinct groups of enzymes that attack connective tissue proteins. Desnuelle has documented the properties of pancreatic lipase, an enzyme that he carefully distinguishes from e&erases, especially by its requirement for an emulsified substrate. The iron prophyrin proteins whose similar spectral characteristics fall within those defined for Group A are described in an article by Lemberg. While the structure of the heme and many of the biological properties of these compounds have not been established (for example, the existence of a cytochrome a3 is st,ill the subject of controversy), the evidence and arguments are fully and fairly presented to give an appreciat,ion of the present status of these obriously important pigments. A brief paper by Wagner and Folkers summarizes the history of mevalonic acid during the five years since its discovery. Since the biochemistry of trrpene synthesis was described in detail
BOOK in the previous volume, it is reasonable that the present article is restricted to the chemistry of mevalonic acid. Some aspects of protein chemistry are reviewed in two articles by workers in Japan. Mizushima and Shimanouchi have presented some of the factors involved in the determination of the configurat,ion of polypeptide chains. Snalogies with simple models have led to the description of several configurations whose stabilities can be compared. The article concludes, however, with a recognition of the controlling role of the specific amino acid chains, &lose effects have not yet been analyzed. Okunuki has summarized in detail his analyses of protein configuration, based primarily on sensitivity of various preparations of protein to hydrolysis by an enzyme crystallized from Bacillus subtilis. A novel mathematical analysis of enzyme re-
557
REVIEWS
actions by Christiansen purports to show how rcactions in solution can proceed in discontinuous steps. The model proposed, in which the enzyme molecules in a given solution act synchronously and in which reverse reaction steps are considered to have no activation energy, will probably be found by most investigators to have little applicability to the enzyme systems they are studying. These considerat,ions seem more relevant than the mathematics of the article and convince this reviewer that periodicity in biological reactions must be explained with the use of factors that do not occur in simple enzymic reactions. The broad range of authoritative reviews includcd in this volume will commend it to all who harr found previous volumes of this series to be an effective means for retaining an orientation in the rapidly expanding field of enzymology.
ALMS H. MEHLER, Bethesda,
Maryland