Ira Katz

On the probable origin of some milk fat acids in rumen microbial lipids

The quantity and character of the microbial lipid isolated from rumen digesta are interpreted as indicating that significant quantities of milk fat acids originate from rumen microbial synthesis of long chain acids from volatile fatty acids. Component fatty acid patterns are presented of rumen bacterial lipid, crude rumen protozoal lipid, blood serum lipid, and milk lipid isolated from samples taken from a lactating Holstein. Certain rumen bacterial lipid fractions are shown to be very rich sources of odd carbon acids and branched acids, and it is suggested that the major source of these acids in ruminant fats is from bacterial synthesis rather than animal synthesis.

Studies on phenylalanine and tyrosine hydroxylation by rat brain tyrosine hydroxylase.

Tyrosine hydroxylase (EC1.14.16.2), presumably the rate-limiting enzyme in the biosynthesis of catecholamines, is known to catalyze the hydroxylation of both phenylalanine and tyrosine. Using both an isolated enzyme preparation and a synaptosomal preparation, where some architectural integrity of the tissue has been preserved, we have attempted to evaluate the manner in which these two substrates are hydroxylated by rat brain tyrosine hydroxylase. In the presence of tetrahydrobiopterin the isolated enzyme catalyzes the hydroxylation of phenylalanine to 3,4-dihydroxyphenylalanine with the release of free tyrosine as an obligatory intermediate. In contrast, the rat brain striatal synaptosomal preparation in the presence of endogenous cofactor converts phenylalanine to 3,4-dihydroxyphenylalanine without the release of free tyrosine.

Activation of tyrosine hydroxylase by polyanions and salts. An electrostatic effect.

The activity of a partially purified preparation of tyrosine hydroxylase (EC 1.14.16.2) from the bovine caudate nucleus was increased by heparin, chondroitin sulfate, phosphatidylserine, polyacrylic acid, polyvinyl sulfuric acid and both poly-D-, and poly-L-glutamic acids, all polyanions. A variety of salts both activated the enzyme and prevented the activation by the polyanions. The observations that activity is increased when the enzyme interacts with salts and with macromolecules of high negative charge density are used to infer a model for these interactions and for the structural change in the enzyme that accompanies activation.

The lipids of some rumen holotrich protozoa

Abstract The lipids from rumen holotrich protozoa were isolated and partially identified. The lipid consisted of 70% phospholipids and 30% non-phospholipids. The phospholipids contained phosphatidyl ethanolamine (21%), phosphatidyl ethanolamine plasmalogen (22%), phosphatidyl choline (28%), and unknown phospholipids (29%). All the phospholipid fractions contained significant amounts of branched chain and unsaturated fatty acids. Degradation of the phosphatidyl ethanolamine and phosphatidyl choline with phospholipase A revealed that the branched chain and unsaturated acids were located in the beta position. Chemical degradation of the phosphatidyl ethanolamine plasmalogen indicated that the vinyl ether linkage was in the alpha position. The non-phospholipids consisted of a mixture of waxes, hydrocarbons, aliphatic alcohols, diglycerides, monoglycerides, hydroxyacids, unesterified fatty acids and sterols. The sterols and unesterified fatty acids comprised 50% of the fraction. The low concentration of stearic acid in the unesterified fatty acids (8.3%) raises a question as to the quantitative importance of holotrich protozoa in rumen hydrogenation.

The isolation of fatty aldehydes from rumen-microbial lipid

Abstract 1. 1. The isolation of fatty aldehydes (as 2,4-dinotrophenylhydrozones) from the bacterial fraction of rumen digesta is described. 2. 2. Mixed rumen bacteria are a rich source of aldehydrogenic lipid as indicated by an aldehyde/phosphorus ration of 0.19 in the non-dialyzable lipid, and the yielding of 2.2. g of aldehyde (calculated as pentadecanal) per 100 g of total bacterial lipid. 3. 3. The major bacterial aldehydes are palmitaldehyde and C 15 branched-chain aldehydes. 4. 4. The aldehyde pattern of rumen bacteria is strikingly similar to the aldehyde patterns in certain ruminant lipids suggesting a possible origin of some ruminant aldehydes in the bacteria.