1. Succinate dehydrogenase flavocoenzyme (“SD-flavin”), previously shown to be an SOLsubstituted riboflavin derivative containing a tertiary nitrogen homoconjugated to the flavin nucleus, was subjected to further hydrolysis and to reduction under acid conditions. Both conditions resulted in the liberation of 1 mole of histidine per mole of flavin. This proves histidine to be the covalent link between flavin and peptide backbone in succinate dehydrogenase and imidazole to be the tertiary nitrogen function homoconjugated to the flavin. 2. 8a-Histidyl-riboflavin has been synthesized starting from riboflavin chemically and shown to be completely identical with the natural product in optical, ESR and NMR spectra, pH-fluorescence curve and behavior on thin-layer and paper chromatography, as well as paper electrophoresis. CH,OH

Studies on succinate dehydrogenase. 8 -Histidyl-FAD as the active center of succinate dehydrogenase.

Factors that determine the reactivity toward iodine of the histidyl residues of various proteins are compared. The proteins studied include lysozyme, ribonuclease, insulin, lactic, malic and glutamic dehydrogenases, phosphoglucomutase, thyroglobulin, trypsin, chymotrypsin and β-lactoglobulin. Relatively fewer histidyl residues than tyrosyl residues are iodianated at pH 8.5 both in water and in guanidine. The fraction of iodine present in histidyl residues increases with increasing pH. Diiodohistidine is formed primarily in proteins that do not contain tryptophane.



Thyroglobulin can be iodinated to contain 8% histidine iodine. However, mono- and diiodohistidine formation in equilibrium-labelled thyroids accounts for < 1% of the total iodine.



Histidine iodination requires the dissociable proton of the imidazole ring as shown by lack of iodination of N-methylated model compounds. The assumption that iodination proceeds by an attack on the imidazole anion (rather than via an N-I intermediate) is supported by the finding that the sterically hindered 2-t-butyl imidazole is iodinated.



It is concluded that, although conformational factors such as electrostatic facilitation and ligand binding influence the reactivity of certain histidyl residues, the major factors in histidyl iodination are the instrinsic properties of the residue.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1969.tb00618.x

Factors in the iodination of histidine in proteins.

Analysis of histidine-containing dipeptides, polyamines, and related amino acids by high-performance liquid chromatography: Application to guinea pig brain

The amounts of anserine (β-alanyl-L-1-methylhistidine), carnosine (β-alanyl-L-histidine) and ophidine (β-alanyl-L-3-methylhistidine) were determined in various muscles and other tissues of pigs. The amount of the histidine dipeptides varied with age and muscle type. Ophidine accumulated in the longissimus dorsi at a rate of 25 nmol g−1 protein day−1 while the anserine concentration remained relatively constant. Thus, an estimate of the age of a pig can be obtained from the anserine: ophidine ratio in a sample of its skeletal muscle. Because the histidine dipeptides are unaffected by cooking, it is possible from an analysis of the dipeptides to monitor the type of lean pig meat used in preparing tinned hams. As the anserine:carnosine:ophidine ratio in pig meat is quite different from that in other species it is possible to distinguish between genuine and imitation hams.

Ophidine (beta-alanyl-L-3-methylhistidine, Balenine) and other histidine dipeptides in pig muscles and tinned hams

Publisher Summary This chapter describes the distribution, metabolism, and physiological function of histidine-related dipeptides. Animal tissue has long been known to contain quite a few different types of L-histidine-related dipeptides (imidazole dipeptides). The dipeptides refer to carnosine, anserine, balenine, and homocarnosine. Of these dipeptides, carnosine, anserine, and balenine may occur in the vertebrate skeletal muscle in large amounts depending on the species. Although the distribution of the dipeptides is restricted in the muscle of invertebrate and most white-fleshed fishes, such as percid and pleuronectid fishes, large amounts of these dipeptides are found in the wide variety of vertebrate muscles. Their distribution, however, lacks any phylogenetic basis. Balenine, for instance, which is found only in trace amount in most vertebrate muscles, is abundant in the muscle of snakes and whales. Camosine is rather common in vertebrate muscles, but some fishes and birds contain much higher amounts of anserine than camosine. The chapter discusses the distribution of free L-histidine and related dipeptides in fish tissues and elaborates the effects of physiological conditions on the dipeptide concentrations in the fish muscle.

Chapter 14 Histidine-related dipeptides: distribution, metabolism, and physiological function

On the structure of ophidine.

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On the structure of ophidine.