Norman R. Lazarus

A monomeric insulin from the porcupine (Hystrix cristata), an Old World hystricomorph

The insulins of New World hystricomorph rodents exhibit many novel amino acid changes in primary structure when compared with other mammalian insulins1–3. These changes give rise to unusual properties (low potency, failure to self-associate4–6) not shared by other naturally-occurring insulins. We report here on the primary structure, zinc-binding properties and circular dichroism (CD) of porcupine insulin (Hystrix cristata), the first Old World hystricomorph insulin to be investigated, and discuss the changes in primary structure of the hormone in relation to its properties. Residue B22 is strongly implicated as being responsible for the unusual properties of porcupine insulin.

Regulation of 3′,5′-cyclic AMP-dependent protein kinase in the plasma membrane of cod (Gadus callarius) and mouse islets

SummaryThe membranes of both mouse and cod islets contain a protein phosphokinase enzyme. 3′,5′-cyclic AMP, ouabain, phosphoenolpyruvate and glucose-6-phosphate enhance protein phosphokinase activity. Protein kinase which is membrane bound is unable to use exogenous protein (histone) as a substrate and phosphorylates specific proteins in the membranes. These proteins have been partially characterized.

An in vitro system for studying insulin release: effects of glucose and glucose‐6‐phosphate

1. Investigation of the ionic requirements of the in vitro insulin release system, which consists of cod islet plasma membrane and rabbit islet granules incubated at pH 6.5, showed that the presence of Ca2+ was obligatory for the system to operate.