Sigmund Schwimmer

Characterization of alliinase of Allium cepa (onion).

Abstract Various procedures for the preparation of protein fractions from onion, capable of converting S-alkyl- l -cysteine sulfoxides to ammonia, pyruvate, and alkyl alkane thiosulfinates are described. The identity of alliinase-produced carbonyl as pyruvic acid was established by the infrared spectrum of its 2,4-dinitrophenylhydrazone and by coupling alliinase action to lactic dehydrogenase via reduced diphosphopyridine nucleotide. The enzyme acted maximally in the presence of pyridoxal phosphate and pyrophosphate buffer at pH 8.5–8.8, is very unstable at acid pHs, and possesses a Km of about 4 × 10−3M with (±)) S-propyl- l -cysteine sulfoxide as substrate. Evidence is presented for the role of pyridoxal phosphate as coenzyme of alliinase. The presence of the l -cysteine moiety and the sulfoxide grouping are absolute requirements for substrate specificity. The dextrarotatory diastereomers of the S-substituted l -cystine sulfoxides were hydrolyzed more rapidly than were the corresponding levorotatory forms. The unresolved S-propyl derivative was hydrolyzed faster than were both the S-methyl and most synthetic preparations of S-allyl derivatives employed. A quantitative method for the determination of thiolsulfinates is presented.

Degradation of tomatine to 3β-hydroxy-5α-pregn-16-en-20-one by ripe tomatoes

Abstract Tomatine-4- 14 C was prepared by foliar administration of cholesterol-4- 14 C and silicone oil to tomato plants. Chromatographically homogeneous tomatine-4- 14 C in 96% ethanol, when incubated in whole, ripe tomatoes was rapidly converted to 3β-hydroxy-5α-pregn-16-en-20-one in combined form. The identity of this steroid and its acetyl derivative was established by comparing their TCL mobilities with reference materials and by recrystallizing them to constant specific activity.

Caffeine metabolism by Penicillium roqueforti

Abstract A strain of P. roqueforti isolated on caffeine-containing agar from air grew in culture media containing concentrations as high as 0.04 m caffeine as the sole source of nitrogen. Growth was accompanied by complete removal of caffeine from the culture medium. After short incubations of nitrogen-starved inocula of this fungus with caffeine-1-methyl- 14 C or with caffeine-2- 14 C, radioactive theophylline was isolated. It was identified by thin-layer chromatography in three solvent systems and also by reconversion to radioactive caffeine after treatment with dimethyl sulfate. Thus, the first step in the metabolism of caffeine by P. roqueforti involves demethylation in the 7-position.

Caffeine removal from growth media by microorganisms

Bacillus coagulans sowie 2 Pilze,Penicillium roqueforti und eineStemphylium-Spezies wurden auf Nährböden isoliert, welche Kaffein als einzige Quelle für Kohlenstoff und Stickstoff enthalten. Diese Mikroorganismen vermehren sich mit derselben Geschwindigkeit auf Kaffein- wie auf Nitratmedien. Dieser Kaffein-Katabolismus wäre möglicherweise der Weg, um die Giftigkeit und mutagenen Wirkungen von Kaffein zu verhindern.

Characterization of S-propenyl-l-cysteine sulfoxide as the principal endogenous substrate of l-Cysteine sulfoxide lyase of onion

Abstract The infrared and ultraviolet absorption spectra of the precursor to the lachrymator trans -(+)- S -propenyl- l -cysteine sulfoxide in onion are presented. This amino acid is converted to pyruvic acid by the l -cysteine sulfoxide lyase of a particulate fraction of onion and by the l -cysteine C-S lyase of Albizzia lophanta. The kinetic constants for this reaction and the fact that this substrate is the preponderant l -cysteine sulfoxide derivative in onion demonstrate that it is the principal endogenous substrate for the onion l -cysteine sulfoxide C-S lyase. Evidence is given for the presence in enzyme reaction mixtures of elemental sulfur previously postulated as a product of the enzyme reaction but not of propionaldehyde or 2-methyl-2-pentenal previously found in the vapor above such reaction mixtures. It is concluded that the reaction products comprise a complex mixture of substances derived from the primary sulfur-containing enzymatic product, 1-propenyl sulfenic acid.

Interrelation among measurements of browning of processed potatoes and sugar components

SummaryA principal factor in assessment of quality of processed potato products is the Maillard-reaction-induced brown color which develops during processing (chips) or during subsequent storage (dehydrated dice). The present paper constitutes a statistical appraisal of the relationship between this browning and the individual reducing-sugar components of the raw tubers and dehydrated potato dice. Although correlation coefficients were greater than 0.9 (except for sucrose) comparison of standard errors of estimate and application of a parameter referred to herein as the “discriminatory index” reveals that sugar measurements, or combinations thereof, do not yield sufficient information to establish an exclusively complete causal relationship between reducing sugar components and extent and rate of browning. This is true despite the control or elimination of several factors usually overlooked in the pertinent measurements which might lead to the observed scatter. Possible auxiliary factors operating during the browning reaction, other than sugars and amino compounds, are discussed. Application of discriminatory indices to the data reveals reducing-sugar and glucose measurements as a more sensitive index of browning in potato chips than of browning rate of dehydrated potato dice. On the other hand, measurements of fructose and total sugar constitute equally reliable indices of both types of browning but at a lower sensitivity level. From the standpoint of prediction of quality of processed potato products in general, this analysis leads to the conclusion that subjective or semiquantitative appraisal of chip color may constitute at least as adequate an index of quality as any of the more elaborate objective measurements undertaken in the laboratory.

Nucleohistone as template for the replication of DNA

Abstract The nucleohistone component of pea embryo chromatin is effective in the support of DNA-dependent DNA synthesis although it is totally ineffective in the support of DNA-dependent RNA synthesis. Presence of histone decreases the rate and extent of DNA synthesis. The requirements for DNA synthesis and the DNA synthesized with nucleohistone as template are similar to requirements and product synthesized with deproteinized DNA as template. These results show that DNA can be replicated while complexed as nucleohistone and suggest the histone moiety may play a role in regulating the extent of DNA synthesis.

Chlorophyll formation in potato tubers as influenced by gamma irradiation and by chemicals

SummaryGamma ray dosages of the order of magnitude of 10 kilorads inhibit the formation of chlorophyll in illuminated potato tubers. Increasing doses to 250 kilorads, while further decreasing chlorophyll formation, did not completely suppress it. Tubers treated with the lower doses retained their residual ability to develop chlorophyll upon illumination after a period of dark storage during which the non-irradiated controls lost a significant fraction of theirs. Of the three chemicals applied to the surface of potato tubers chloroisopropyl phenyl carbamate, O-methyl threonine, and 3-amino-1 2, 4-triazole, only the last named one inhibited the development of chlorophyll. Tubers obtained from plants whose leaves had been sprayed with maleic hydrazide developed as much chlorophyll as corresponding controls. Reflectance spectra of the exposed green surface of potato tubers suggest that carotenoid synthesis may be less sensitive to gamma irradiation than is the concomitant development of chlorophyll.

Enzymatic conversion of trans-(+)-S-1-propenyl-l-cysteine S-oxide to the bitter and odor-bearing components of onion

Abstract Trans -(+)- S -1-Propenyl- l -cysteine S -oxide, hitherto reported to be enzymatically transformed into the lachrymatory substance of freshly comminuted onion tissue, has now also been found to be the sole precursor of the substance responsible for the bitter taste in onion macerates. From a consideration of its concentration in onion, its properties as a substrate for enzyme action, and the relatively strong sensory responses elicited from such enzyme action, it is concluded this propenyl derivative is to a large degree responsible for the development of all of the sensory attributes perceived upon comminution of onion tissue.

Gamma irradiation of potatoes: Effects on sugar content, chip color, germination, greening, and susceptibility to mold

Russet Burbank potatoes that had been stored at 40°F. for 5 months after harvest were irradiated with 5,200 and 14,000 rad of Co60 gamma rays. In general, irradiation caused an accumulation of sugars. At 40°F., the sucrose level rose to nearly 3 times that of the control in 16 days following irradiation. Fructose and glucose showed smaller increases and the latter did not accumulate significantly in the tubers given the higher dose of gamma rays. At 70°F., the levels of sucrose and glucose in the irradiated tubers rose above those in the controls, the difference reaching a maximum in 4 days and then declining. Irradiation had no effect on loss of fructose at this temperature. Color of potato chips processed from the irradiated potatoes was in general darker than that of chips from control tubers. The storage-time pattern of color change resembled that of the reducing rather than total sugar. Fourteen thousand rad did not prevent initiation of germination in the tubers but did destroy their sprout-growth apparatus. Although the lower dosage did not prevent initiation and subsequent growth, it prevented the formation of secondary tubers, which appeared on the sprouted control tubers. Furthermore, unlike the controls, the low-dosage potatoes developed branching hair sprouts with no tendency toward apical dominance during the early stages of sprouting. The rate of greening of gamma-irradiated and illuminated tubers was significantly less than that of unirradiated illuminated controls. Evidence is presented that irradiation may increase the susceptibility of potatoes to attack by molds under some conditions.